feat: 8 AI providers, rich text editor, agent notifications, UI contrast & font settings

- Add DeepSeek, OpenRouter, Mistral, Z.AI, LM Studio as AI providers
  with editable model names via Combobox in admin settings
- Fix OpenRouter broken by normalizeProvider bug in config.ts
- Convert agent-created notes from Markdown to HTML (TipTap rich text)
- Add Notification model + in-app notifications for agent results
- Agent notification click opens the created note directly
- Add note count display on notebook and inbox headers
- Fix checklist toggle in card view (persist state via localCheckItems)
- Add checklist creation option in tabs/list view (dropdown on + button)
- Fix image description ENOENT error with HTTP fallback
- Improve UI contrast across all themes (input, border, checkbox visibility)
- Add font family setting (Inter vs System Default) in Appearance settings
- Fix CSS font-sans variable conflict (removed dead Geist references)
- Update README with new features and 8 providers

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

docker-compose.yml

@@ -39,6 +39,7 @@ services:
       - DATABASE_URL=postgresql://${POSTGRES_USER:-memento}:${POSTGRES_PASSWORD:-memento}@postgres:5432/${POSTGRES_DB:-memento}
       - NODE_ENV=production
       - NEXT_TELEMETRY_DISABLED=1
+      # ADMIN_EMAIL comes from .env.docker via env_file directive above
     volumes:
       - uploads-data:/app/data/uploads
       - backup-data:/app/data/backups