feat(ui): add standalone dashboard mode and relay switching (v0.52.2)

- Add standalone mode for dashboard to connect to any ORLY relay
- Implement relay switcher dropdown in header for standalone mode
- Add mobile drawer sidebar at 640px breakpoint with hamburger menu
- Add dedicated fallback pool for profile/relay list/contact list fetches
- Fix relay URL display to show host instead of NIP-11 name
- Add filter validation and defensive checks in event fetching
- Auto-expand search window from 30 days to 6 months on few results
- Add CORS support for API endpoints with configurable origins
- Fetch user relay list (NIP-65 kind 10002) and contact list on login
- Fix light mode user name color visibility in header

Files modified:
- app/config/config.go: Add CORS configuration options
- app/server.go: Add CORS middleware for API endpoints
- app/handle-relayinfo.go: Include CORS in relay info
- app/web/src/config.js: New config module for standalone mode
- app/web/src/stores.js: Add relay URL and standalone mode stores
- app/web/src/nostr.js: Add fallback pool, filter validation, relay/contact fetch
- app/web/src/Header.svelte: Relay dropdown, mobile menu, static indicator
- app/web/src/Sidebar.svelte: Mobile drawer mode with overlay
- app/web/src/App.svelte: Relay switching, mobile menu state, NIP-65 fetch
- app/web/src/api.js: Use configurable base URL
- app/web/src/constants.js: Add fallback relays, dynamic relay URLs
- cmd/dashboard-server/main.go: New standalone dashboard server

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

app/web/bun.lock

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