Add Print Queue UI and slicer post-processing script

- Create Print Queue page showing pending/completed/cancelled jobs
- Add needs_weighing filter to spool API for flagged spools
- Add IPrintJob interface and needs_weighing to ISpool model
- Add slicer_post_process.py for Elegoo/Orca Slicer integration
- Add translations for print queue feature
- Bump version to 0.23C.3

The workflow:
1. Slicer post-processing script creates pending print job
2. After print, user confirms (deducts filament) or cancels (flags for weighing)
3. Spools needing weigh-in are shown in Print Queue UI

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

spoolman/api/v1/spool.py

@@ -264,6 +264,10 @@ async def find(
         bool,
         Query(title="Allow Archived", description="Whether to include archived spools in the search results."),
     ] = False,
+    needs_weighing: Annotated[
+        Optional[bool],
+        Query(title="Needs Weighing", description="Filter by spools that need manual weigh-in."),
+    ] = None,
     sort: Annotated[
         Optional[str],
         Query(
@@ -308,6 +312,7 @@ async def find(
         location=location,
         lot_nr=lot_nr,
         allow_archived=allow_archived,
+        needs_weighing=needs_weighing,
         sort_by=sort_by,
         limit=limit,
         offset=offset,