feat(filament): add spool count and total remaining weight columns

Adds computed spool statistics to filament list:
- spool_count: Number of non-archived spools of this filament
- total_remaining_weight: Sum of remaining weight across all spools

Backend changes:
- Modified database/filament.py find() to compute stats via subquery
- Added fields to Filament pydantic model in api/v1/models.py
- Updated filament API endpoint to include stats in response

Frontend changes:
- Added fields to IFilament interface
- Added columns to filament list table
- Added translation keys

Closes #15

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

spoolman/api/v1/filament.py

@@ -366,7 +366,7 @@ async def find(
     else:
         filter_by_ids = None
 
-    db_items, total_count = await filament.find(
+    db_items, total_count, spool_stats = await filament.find(
         db=db,
         ids=filter_by_ids,
         vendor_name=vendor_name if vendor_name is not None else vendor_name_old,
@@ -383,7 +383,14 @@ async def find(
     # Set x-total-count header for pagination
     return JSONResponse(
         content=jsonable_encoder(
-            (Filament.from_db(db_item) for db_item in db_items),
+            (
+                Filament.from_db(
+                    db_item,
+                    spool_count=spool_stats.get(db_item.id, (0, 0))[0],
+                    total_remaining_weight=spool_stats.get(db_item.id, (0, 0))[1],
+                )
+                for db_item in db_items
+            ),
             exclude_none=True,
         ),
         headers={"x-total-count": str(total_count)},