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/models.py

@@ -221,9 +221,25 @@ class Filament(BaseModel):
             "Query the /fields endpoint for more details about the fields."
         ),
     )
+    spool_count: Optional[int] = Field(
+        None,
+        ge=0,
+        description="Number of spools of this filament (excluding archived). Computed field.",
+        examples=[5],
+    )
+    total_remaining_weight: Optional[float] = Field(
+        None,
+        ge=0,
+        description="Total remaining weight across all spools of this filament (excluding archived), in grams. Computed field.",
+        examples=[2500.0],
+    )
 
     @staticmethod
-    def from_db(item: models.Filament) -> "Filament":
+    def from_db(
+        item: models.Filament,
+        spool_count: Optional[int] = None,
+        total_remaining_weight: Optional[float] = None,
+    ) -> "Filament":
         """Create a new Pydantic filament object from a database filament object."""
         return Filament(
             id=item.id,
@@ -251,6 +267,8 @@ class Filament(BaseModel):
             ),
             external_id=item.external_id,
             extra={field.key: field.value for field in item.extra},
+            spool_count=spool_count,
+            total_remaining_weight=total_remaining_weight,
         )