Fix settings route switching and document API token system ...

- App.vue: make route reactive via ref + getRouteFromHash() so
  #settings toggles work without page reload
- docs/api_tokens.md: new comprehensive API token auth doc
- docs/api.md: add /api-tokens REST endpoints
- docs/auth.md: add token flow architecture diagram and resolution order
- docs/websocket.md: add auth section with cookie vs query-param token
- docs/architecture.md: update to AgentSessionOrchestrator + ToolContext
- docs/tools.md: add gnexus-creds MCP tools
- docs/index.md: link to api_tokens.md
- Rebuild webclient dist

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

Document Android OAuth bridge page flow ...

- docs/auth.md: describe browser vs Android WebView flows, bridge page
  mechanism, state metadata detection via NaviAndroid UA
- docs/api.md: add /auth/mobile-done endpoint reference
- docs/android-client.md: add OAuth/login section covering intent filter,
  CookieManager injection, deep-link handling in onCreate/onNewIntent

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

Revert "Fix avatar: use Gravatar instead of non-existent profile fields" ...

This reverts commit f485e54.

Fix avatar: use Gravatar instead of non-existent profile fields ...

Investigated gnexus-auth UserinfoController and found that the profile
response only contains: username, display_name, first_name, last_name,
phone, birth_date, country, city, locale, timezone. There is no picture
or avatar_url field.

- Add make_gravatar_url() helper in navi/auth/__init__.py
- Update deps.py to generate Gravatar URL from user email
- Update config.py default gnauth_profile_path to /account/profile
- Update .env.example comment accordingly
- Frontend already handles avatar_url correctly

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

Add legacy data migration script and docs ...

- scripts/assign_legacy_sessions.py assigns user_id=NULL sessions,
  memory_facts, and memory_summary to a target user
  - Handles UNIQUE constraint conflicts in memory_facts by merging
  - Merges memory_summary if user already has one
- Update docs/auth.md with legacy migration section

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

Document multi-user auth system ...

- New docs/auth.md — comprehensive auth guide: OAuth flow, roles/permissions,
  webhooks, env vars, setup instructions, API reference, WebSocket auth,
  testing with mocked auth
- Update docs/config.md — add gnexus-auth OAuth env vars table
- Update docs/api.md — add /auth/*, /admin/*, /webhooks/gnexus-auth endpoints
- Update docs/index.md — add auth.md to file map
- Update docs/sessions.md — document user_id column and list_all filtering
- Update docs/memory.md — document user_id scoping in facts and summaries

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