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>

client/public/locales/en/common.json

@@ -260,7 +260,9 @@
             "longitudinal": "Longitudinal",
             "external_id": "External ID",
             "spools": "Show Spools",
-            "not_set": "Not Set"
+            "not_set": "Not Set",
+            "spool_count": "Spools",
+            "total_remaining_weight": "Total Remaining"
         },
         "fields_help": {
             "name": "Filament name, to distinguish this filament type among others from the same manufacturer. Should contain the color for example.",