feat: Add smart density defaults based on material type (#2)

Auto-fill density when entering material type in filament forms:
- Add materialDefaults.ts with standard densities for common materials
  (PLA, ABS, PETG, TPU, PC, etc.)
- Material field now uses AutoComplete with suggestions
- Density auto-fills on material select or blur (fuzzy matching)
- New filaments default to 1.75mm diameter and 1.24 g/cm³ (PLA)
- Applied to both full filament create page and quick create modal

Reduces tedious data entry for common materials while still allowing
custom values for specialty filaments.

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

client/public/locales/en/common.json

@@ -263,7 +263,8 @@
             "import_external_description": "Select a filament in the list to automatically populate its details in the filament creation form. This will overwrite any data you have entered in the form.<br><br>A Manufacturer object will be created automatically when you click Ok, if necessary.",
             "created_success": "Created filament \"{{name}}\"",
             "vendor_placeholder": "Select a manufacturer",
-            "name_placeholder": "E.g. Matte Black"
+            "name_placeholder": "E.g. Matte Black",
+            "material_placeholder": "PLA, PETG, ABS, etc."
         },
         "buttons": {
             "add_spool": "Add Spool"