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/database/spool.py

@@ -123,6 +123,7 @@ async def find(  # noqa: C901, PLR0912
     location: Optional[str] = None,
     lot_nr: Optional[str] = None,
     allow_archived: bool = False,
+    needs_weighing: Optional[bool] = None,
     sort_by: Optional[dict[str, SortOrder]] = None,
     limit: Optional[int] = None,
     offset: int = 0,
@@ -158,6 +159,17 @@ async def find(  # noqa: C901, PLR0912
             ),
         )
 
+    if needs_weighing is not None:
+        if needs_weighing:
+            stmt = stmt.where(models.Spool.needs_weighing.is_(True))
+        else:
+            stmt = stmt.where(
+                sqlalchemy.or_(
+                    models.Spool.needs_weighing.is_(False),
+                    models.Spool.needs_weighing.is_(None),
+                ),
+            )
+
     total_count = None
 
     if limit is not None: