feat: Add 3dfilamentprofiles.com integration (Issue #7)

- Backend: Added ExternalSource enum, Filament3DFP model, and transform function
- Backend: Updated _sync() to fetch from both SpoolmanDB and 3dfilamentprofiles
- Frontend: Added source tabs to FilamentImportModal (All/SpoolmanDB/3DFP)
- Frontend: Updated ExternalFilament interface with source and temp range fields
- Frontend: Updated filament import handler to use temp range fields

Also includes:
- Dev mode styling (teal theme, DEV badge and banner)
- Translation keys for source filtering

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

client/public/locales/en/common.json

@@ -276,6 +276,8 @@
             "filament_updated": "This filament has been updated by someone/something else since you opened this page. Saving will overwrite those changes!",
             "import_external": "Import from External",
             "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.",
+            "all_sources": "All Sources",
+            "select_filament": "Select a filament...",
             "created_success": "Created filament \"{{name}}\"",
             "vendor_placeholder": "Select a manufacturer",
             "name_placeholder": "E.g. Matte Black",