● feat(slicer): server-side slicing via OrcaSlicer / Bambu Studio sidecar

Adds an optional slicer-api/ Compose stack and wires Bambuddy's File
  Manager, Archives, and MakerWorld pages to a new server-side Slice flow.
  Slicing runs as an in-memory background job (POST returns 202 + job_id,
  polled via GET /api/v1/slice-jobs/{id}) so a multi-minute slice no
  longer pins the modal; result lands as a new .gcode.3mf in the same
  folder (or new archive for archive sources) with the embedded
  thumbnail extracted.

  Backend
  - New services: slice_dispatch (in-memory dispatcher, 30min retention
    sweep) and slicer_api (HTTP bridge with 4xx/5xx/connection error
    split that drives the 3MF embedded-settings fallback retry path).
  - New schemas: SliceRequest, SliceResponse, SliceArchiveResponse,
    SliceJobEnqueueResponse.
  - New routes: POST /library/files/{id}/slice,
    POST /archives/{id}/slice, GET /api/v1/slice-jobs/{id} (gated on
    LIBRARY_READ since job IDs are sequential and the body leaks source
    filenames and result IDs).
  - AppSettings + env defaults: use_slicer_api, orcaslicer_api_url,
    bambu_studio_api_url. DB-stored values override env defaults.

  Frontend
  - New SliceModal handles preset gating; enqueues then closes
    immediately.
  - New SliceJobTrackerProvider polls active jobs at app level, surfaces
    a single toast per job (queued -> running -> completed / failed)
    and invalidates library/archives queries on terminal status.
  - Settings -> Workflow -> Slicer card: preferred slicer dropdown,
    Use Slicer API toggle, contextual sidecar URL field.
  - File Manager / Archives / MakerWorld get a Slice button gated on
    the Use Slicer API setting.
  - gcode-viewer adapter learns ?library_file=<id> so sliced library
    files preview inline.

  i18n
  - New slice.* and settings.{useSlicerApi,slicerCard,orcaslicerApiUrl,
    bambuStudioApiUrl,slicerApiUrlDescription,useSlicerApiDescription}
    + fileManager.noPermissionSlice keys across all 8 locales (en, de,
    fr, it, ja, pt-BR, zh-CN, zh-TW). English fully translated, German
    fully translated, the other six seeded with English fallbacks
    pending native translation.

  Tests
  - 10 backend integration tests in test_library_slice_api.py covering
    validation (404/400), happy-path enqueue, sidecar-down, 3MF
    embedded-settings fallback, STL no-fallback, and preset-error ->
    failed job paths.
  - New unit tests in test_slicer_api.py for the HTTP bridge.
  - 5 new SliceModal frontend tests covering preset gating, library +
    archive enqueue paths, error surface, and preset-load failure.
  - Existing SettingsPage tests adjusted: slicer dropdown asserts now
    switch to the Workflow tab first; added a beforeEach URL reset so
    one test's tab click doesn't bleed into sibling tests.

  Sidecar
  - New slicer-api/ folder is self-contained and optional. Two services
    (orca-slicer-api on 3003, bambu-studio-api on 3001 behind --profile
    bambu) build via Docker git-build-context from
    maziggy/orca-slicer-api@bambuddy/profile-resolver. The fork patches
    the OrcaSlicer CLI's profile compatibility quirks (inherits-chain
    resolver, from:User -> system rewrite, '# ' clone-prefix strip,
    sentinel-value strip) empirically required to slice real GUI
    exports without segfaulting the CLI.

  Docs
  - CHANGELOG entry under [0.2.4b1] - Unreleased Added.
  - README File Manager bullet for the new server-side Slice button.
  - bambuddy-website features.html: new card under "Configurable Slicer".
  - bambuddy-wiki: new page features/slicer-api.md + nav entry +
    features index card.

  Notes
  - Opt-in: with Use Slicer API off, the existing "open in desktop
    slicer via URI" flow is the default and unchanged.
  - 3MF inputs that segfault the CLI on --load-settings transparently
    retry with embedded settings; the resulting job carries
    used_embedded_settings: true.
  - Sliced files always export as .gcode.3mf so File Manager picks up
    the embedded thumbnail; file_type is set to "gcode" (blue badge).

frontend/src/components/SliceModal.tsx

@@ -0,0 +1,207 @@
+import { Cog, Loader2, X } from 'lucide-react';
+import { useState } from 'react';
+import { useTranslation } from 'react-i18next';
+import { useMutation, useQuery } from '@tanstack/react-query';
+import { api, type LocalPreset } from '../api/client';
+import { useSliceJobTracker } from '../contexts/SliceJobTrackerContext';
+
+export type SliceSource =
+  | { kind: 'libraryFile'; id: number; filename: string }
+  | { kind: 'archive'; id: number; filename: string };
+
+interface SliceModalProps {
+  source: SliceSource;
+  onClose: () => void;
+}
+
+export function SliceModal({ source, onClose }: SliceModalProps) {
+  const { t } = useTranslation();
+  const { trackJob } = useSliceJobTracker();
+
+  const [printerPresetId, setPrinterPresetId] = useState<number | null>(null);
+  const [processPresetId, setProcessPresetId] = useState<number | null>(null);
+  const [filamentPresetId, setFilamentPresetId] = useState<number | null>(null);
+  const [errorMessage, setErrorMessage] = useState<string | null>(null);
+
+  const presetsQuery = useQuery({
+    queryKey: ['localPresets'],
+    queryFn: () => api.getLocalPresets(),
+    staleTime: 60_000,
+  });
+
+  const enqueueMutation = useMutation({
+    mutationFn: async () => {
+      if (printerPresetId == null || processPresetId == null || filamentPresetId == null) {
+        throw new Error('All three presets must be selected');
+      }
+      const body = {
+        printer_preset_id: printerPresetId,
+        process_preset_id: processPresetId,
+        filament_preset_id: filamentPresetId,
+      };
+      if (source.kind === 'libraryFile') {
+        return api.sliceLibraryFile(source.id, body);
+      }
+      return api.sliceArchive(source.id, body);
+    },
+    onSuccess: (enqueue) => {
+      // Hand the job off to the global tracker — polling, toasts, and
+      // query invalidation continue across navigation.
+      trackJob(enqueue.job_id, source.kind, source.filename);
+      onClose();
+    },
+    onError: (err: unknown) => {
+      const msg = err instanceof Error ? err.message : String(err);
+      setErrorMessage(msg);
+    },
+  });
+
+  const isReady = printerPresetId != null && processPresetId != null && filamentPresetId != null;
+  const isEnqueuing = enqueueMutation.isPending;
+
+  return (
+    <div
+      className="fixed inset-0 z-50 flex items-center justify-center bg-black/60 p-4"
+      onClick={() => {
+        if (!isEnqueuing) onClose();
+      }}
+    >
+      <div
+        className="w-full max-w-xl max-h-[85vh] flex flex-col rounded-lg bg-bambu-dark-secondary border border-bambu-dark-tertiary/60"
+        onClick={(e) => e.stopPropagation()}
+      >
+        {/* Header */}
+        <div className="flex-shrink-0 flex items-start justify-between gap-3 px-4 pt-4 pb-3 border-b border-bambu-dark-tertiary/40">
+          <div className="min-w-0">
+            <h3 className="text-white font-medium flex items-center gap-2">
+              <Cog className="w-4 h-4" />
+              {t('slice.title', 'Slice model')}
+            </h3>
+            <p className="text-xs text-bambu-gray mt-1 truncate" title={source.filename}>
+              {source.filename}
+            </p>
+          </div>
+          <button
+            onClick={onClose}
+            disabled={isEnqueuing}
+            className="flex-shrink-0 text-bambu-gray hover:text-white transition-colors disabled:opacity-50"
+            aria-label={t('common.close', 'Close')}
+          >
+            <X className="w-5 h-5" />
+          </button>
+        </div>
+
+        {/* Body */}
+        <div className="flex-1 overflow-y-auto p-4 space-y-4">
+          {presetsQuery.isLoading && (
+            <div className="flex items-center gap-2 text-bambu-gray text-sm">
+              <Loader2 className="w-4 h-4 animate-spin" />
+              {t('slice.loadingPresets', 'Loading presets…')}
+            </div>
+          )}
+
+          {presetsQuery.isError && (
+            <div className="text-sm text-red-400" role="alert">
+              {t(
+                'slice.presetsLoadFailed',
+                'Failed to load presets. Open Settings → Profiles to import them first.',
+              )}
+            </div>
+          )}
+
+          {presetsQuery.data && (
+            <>
+              <PresetDropdown
+                label={t('slice.printer', 'Printer profile')}
+                presets={presetsQuery.data.printer}
+                value={printerPresetId}
+                onChange={setPrinterPresetId}
+                disabled={isEnqueuing}
+              />
+              <PresetDropdown
+                label={t('slice.process', 'Process profile')}
+                presets={presetsQuery.data.process}
+                value={processPresetId}
+                onChange={setProcessPresetId}
+                disabled={isEnqueuing}
+              />
+              <PresetDropdown
+                label={t('slice.filament', 'Filament profile')}
+                presets={presetsQuery.data.filament}
+                value={filamentPresetId}
+                onChange={setFilamentPresetId}
+                disabled={isEnqueuing}
+              />
+            </>
+          )}
+
+          {errorMessage && (
+            <div className="text-sm text-red-400 bg-red-900/20 border border-red-900/40 rounded p-2" role="alert">
+              {errorMessage}
+            </div>
+          )}
+        </div>
+
+        {/* Footer */}
+        <div className="flex-shrink-0 flex justify-end gap-2 px-4 py-3 border-t border-bambu-dark-tertiary/40">
+          <button
+            type="button"
+            onClick={onClose}
+            disabled={isEnqueuing}
+            className="px-3 py-1.5 text-sm rounded-md border border-bambu-dark-tertiary text-bambu-gray hover:text-white hover:border-bambu-gray transition-colors disabled:opacity-50"
+          >
+            {t('common.cancel', 'Cancel')}
+          </button>
+          <button
+            type="button"
+            onClick={() => {
+              setErrorMessage(null);
+              enqueueMutation.mutate();
+            }}
+            disabled={!isReady || isEnqueuing}
+            className="px-3 py-1.5 text-sm rounded-md bg-bambu-green hover:bg-bambu-green/90 text-bambu-dark font-medium transition-colors disabled:opacity-50 disabled:cursor-not-allowed flex items-center gap-2"
+          >
+            {isEnqueuing ? (
+              <>
+                <Loader2 className="w-4 h-4 animate-spin" />
+                {t('slice.enqueuing', 'Submitting slice job…')}
+              </>
+            ) : (
+              t('slice.action', 'Slice')
+            )}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}
+
+interface PresetDropdownProps {
+  label: string;
+  presets: LocalPreset[];
+  value: number | null;
+  onChange: (id: number | null) => void;
+  disabled?: boolean;
+}
+
+function PresetDropdown({ label, presets, value, onChange, disabled }: PresetDropdownProps) {
+  const { t } = useTranslation();
+  return (
+    <label className="block">
+      <span className="block text-xs text-bambu-gray mb-1">{label}</span>
+      <select
+        value={value ?? ''}
+        onChange={(e) => onChange(e.target.value ? Number(e.target.value) : null)}
+        disabled={disabled}
+        className="w-full px-3 py-2 rounded-md bg-bambu-dark border border-bambu-dark-tertiary text-white text-sm focus:outline-none focus:border-bambu-gray disabled:opacity-50"
+      >
+        <option value="">{t('slice.selectPreset', '— Select a preset —')}</option>
+        {presets.map((p) => (
+          <option key={p.id} value={p.id}>
+            {p.name}
+          </option>
+        ))}
+      </select>
+    </label>
+  );
+}