feat(metadata): add CivArchive API toggle and provider fallback order settings

- Add enable_civarchive_api toggle (default on) to allow disabling
  CivArchive to avoid its rate-limit windows entirely
- Add metadata_provider_order dropdown with two presets:
  CivitAI → CivArchive → Archive DB (default) and
  CivitAI → Archive DB → CivArchive
- Wire both settings through backend (metadata_service, settings_manager,
  misc_handlers) and frontend (SettingsManager, state, settings modal)
- Reorder Metadata section in settings modal: toggles → status/management
  → fallback order, for natural top-down workflow
- Make update_metadata_providers() log the effective provider chain
  using actually-registered providers rather than settings assumptions
- Add 5 test cases covering all provider-combination paths
- Complete i18n translations for 6 new keys across all 9 non-English locales

py/routes/handlers/misc_handlers.py

@@ -1570,7 +1570,11 @@ class SettingsHandler:
                 else:
                     self._settings.set(key, value)
 
-                if key == "enable_metadata_archive_db":
+                if key in (
+                    "enable_metadata_archive_db",
+                    "enable_civarchive_api",
+                    "metadata_provider_order",
+                ):
                     await self._metadata_provider_updater()
 
                 if key in self._PROXY_KEYS: