feat: dual external spool support, AMS slot model filtering & pre-population

Backend:
- Add dual external spool support for H2D (vt_tray as list: Ext-L/Ext-R)
- Add cloud filament ID map endpoint (/cloud/filament-id-map)
- Fix RFID spool data erased by periodic AMS updates (skip tag matcher
  for RFID-tagged trays)
- Fix AMS slot config overwrites RFID spool state
- Fix K-profile selection corrupts existing profiles on X1C/P1S
- Resolve K-profiles filament name via cloud filament ID map
- Update print scheduler and usage tracker for dual external spools

Frontend:
- Add printer model filtering to ConfigureAmsSlotModal (cloud/local/builtin
  presets filtered by @BBL model suffix and compatible_printers)
- Add pre-population for configured slots (preset, color, K-profile)
- Add K-Profiles view with accurate filament name resolution
- Internationalize all ConfigureAmsSlotModal strings (en/de/fr/it/ja — 21 keys)
- Add 5 new ConfigureAmsSlotModal tests (model filtering, pre-selection,
  color pre-population, i18n)
- Update PrintersPage for dual external spool rendering

Docs:
- Update CHANGELOG, README, website features, and wiki AMS docs

backend/app/services/usage_tracker.py

@@ -263,8 +263,13 @@ async def _track_from_3mf(
     tray_now_override: int | None = None
     if not slot_to_tray and len(nonzero_slots) == 1:
         state = printer_manager.get_status(printer_id)
-        if state and state.tray_now < 255:
+        if state and 0 <= state.tray_now <= 254:
             tray_now_override = state.tray_now
+        elif state and state.tray_now == 255:
+            # 255 = "no filament" on legacy printers, but valid 2nd external spool on H2-series
+            vt_tray = state.raw_data.get("vt_tray") or []
+            if any(int(vt.get("id", 0)) == 255 for vt in vt_tray if isinstance(vt, dict)):
+                tray_now_override = state.tray_now
 
     # Scale factor for partial prints (failed/aborted)
     if status == "completed":
@@ -322,7 +327,11 @@ async def _track_from_3mf(
                 if isinstance(mapped, int) and mapped >= 0:
                     global_tray_id = mapped
 
-        if global_tray_id >= 128:
+        if global_tray_id >= 254:
+            # External spool: ams_id=255 (sentinel), tray_id=slot index (0 or 1)
+            ams_id = 255
+            tray_id = global_tray_id - 254
+        elif global_tray_id >= 128:
             ams_id = global_tray_id
             tray_id = 0
         else: