- Add navi_auth_enabled setting (default true) to navi/config.py and .env.example
- When disabled, treat every request as anonymous admin user (id='anonymous')
- Create/update fixed anonymous navi_users row on startup
- Bypass OAuth/cookie/API-token resolution in navi/auth/deps.py
- Update /auth/status to return {enabled, configured}
- Log security warning on startup when auth is disabled
- Update webclient: skip fetchMe/login screen, show Local mode footer,
  expose /admin link, warn in API keys panel
- Rebuild webclient production bundle
- Add unit and integration tests for no-auth mode
- Update docs: auth.md, config.md, api.md, api_tokens.md, sessions.md,
  websocket.md, mechanics.md, index.md

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

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Backend:
- navi/auth/deps.py: replace 3 DB round-trips with single JOIN query for
  token resolution; update last_used_at still separate (best-effort)
- navi/api/routes/api_tokens.py: replace asyncpg-specific "UPDATE 1"
  string check with RETURNING id fetchrow; increase token_prefix from
  8 to 12 chars for better visual identification; add security notes
- tests/unit/auth/test_api_tokens.py: update tests for JOIN query and
  RETURNING-based revoke

Frontend:
- webclient/src/components/settings/ShowTokenModal.vue: new modal that
  shows the plain token in a readonly field with copy button and
  explicit warning — replaces the transient toast notification
- webclient/src/components/settings/ApiKeysPanel.vue: use ShowTokenModal
- webclient/src/composables/useWebSocket.js: add security comment about
  localStorage XSS risk and query param log exposure

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Backend:
- navi/auth/_ddl.py: add api_tokens table with boot-time migration
- navi/auth/deps.py: _resolve_user now falls back to X-Api-Token header
  and ?api_token query param for WebSocket auth
- navi/auth/__init__.py: add ApiToken pydantic model
- navi/api/routes/api_tokens.py: CRUD endpoints (POST/GET/DELETE)
- navi/main.py: wire api_tokens router

Frontend:
- webclient/src/App.vue: add #settings hash routing
- webclient/src/components/settings/: SettingsView, ApiKeysPanel,
  CreateKeyModal with copy-to-clipboard flow
- webclient/src/api/index.js: token CRUD API functions
- webclient/src/stores/apiTokens.js: Pinia store
- webclient/src/components/sidebar/AppSidebar.vue: settings link
- webclient/src/composables/useWebSocket.js: append ?api_token= when
  localStorage token is present

Tests:
- tests/unit/auth/test_api_tokens.py: 10 unit tests covering token
  resolution (header + query param), revoke, missing/revoked tokens,
  orphan users, and CRUD endpoints

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>