feat(slice-modal): Bundle tier for picking presets from imported .bbscfg

Closes the loop on the bundle work: users who imported a Printer
  Preset Bundle via Settings → Slicer Bundles can now pick it in the
  SliceModal and slice through the bundle dispatch path the backend
  already supports.

  UX:
  - New "Slicer bundle" picker at the top of the modal, rendered only
    when at least one bundle is imported (GET /slicer/bundles non-empty)
  - Selecting a bundle replaces cloud/local/standard preset dropdowns
    with bundle-scoped pickers (process + per-slot filament names from
    the bundle). Printer is implicit (each .bbscfg has exactly one).
  - Submit routes through SliceRequest.bundle so the backend skips
    PresetRef resolution and asks the sidecar to materialise the JSON
    triplet from the stored bundle by name.
  - "None" leaves the modal on the original preset triplet path.

  Frontend types: SliceBundleSpec + bundle?: SliceBundleSpec on SliceRequest.

static/index.html

@@ -26,8 +26,8 @@
 
     <!-- Splash screens for iOS -->
     <link rel="apple-touch-startup-image" href="./img/android-chrome-512x512.png" />
-    <script type="module" crossorigin src="./assets/index-B--K0Euf.js"></script>
-    <link rel="stylesheet" crossorigin href="./assets/index-CzFVl3Rw.css">
+    <script type="module" crossorigin src="./assets/index-D-Dvx81t.js"></script>
+    <link rel="stylesheet" crossorigin href="./assets/index-DmnG_wF0.css">
   </head>
   <body>
     <div id="root"></div>