Add Anthropic API integration, remove locale settings UI

Anthropic API:
- Add @anthropic-ai/sdk with adapter wrapping OpenAI-shaped interface
- Support Claude models (opus, sonnet, haiku) with extended thinking
- Auto-reset model on provider switch, JSON retry logic
- Add Claude model pricing to ai-usage tracker
- Update AI settings form with Anthropic provider option
- Add provider field to AIUsageLog for cross-provider cost tracking

Locale Settings Removal:
- Strip Localization tab from admin settings (mobile + desktop)
- Remove i18n settings from router and feature flags
- Remove LOCALIZATION from SettingCategory enum
- Keep franc document language detection intact

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -21,6 +21,7 @@
     "test:e2e": "playwright test"
   },
   "dependencies": {
+    "@anthropic-ai/sdk": "^0.78.0",
     "@auth/prisma-adapter": "^2.7.4",
     "@blocknote/core": "^0.46.2",
     "@blocknote/mantine": "^0.46.2",