fix(mobile): invite join stuck on Connecting — URL scheme mismatch

[alvinjaison]

Summary

Fixes the iOS invite join flow getting permanently stuck on "Connecting…" when opening a hosted-community invite link.

Root Cause

The invite deep-link parser produces wss:// relay URLs (correct for the WebSocket scheme). These are stored directly as Community.relayUrl. However, RelayConfig.wsUrl assumed baseUrl was always HTTP-scheme:

// Before: only recognized https → wss
final scheme = uri.scheme == 'https' ? 'wss' : 'ws';

When baseUrl was wss://, this incorrectly downgraded it to ws:// (plaintext). A hosted relay at *.communities.buzz.xyz only accepts TLS connections, so the ws:// connect attempt hangs forever — no timeout on WebSocketChannel.connect.

The pairing flow works because it validates and stores URLs as https://, which the old getter handled correctly.

Fix

1. RelayConfig.wsUrl — switch expression that passes wss/ws through unchanged and converts https → wss, http → ws.
2. RelayConfig.httpUrl (new) — inverse getter for REST endpoints. Converts wss → https, ws → http.
3. queryRelay + relayClientProvider — use httpUrl instead of raw baseUrl for HTTP calls (media upload, /query bridge).
4. InviteJoinNotifier.confirmJoin — normalize URL at storage time (wss → https, ws → http) so Community.relayUrl matches the pairing convention.

Testing

• 13 new unit tests for RelayConfig.wsUrl/httpUrl scheme handling
• 2 new parameterized tests for invite URL normalization
• All 20 existing + new invite tests pass
• flutter analyze — no issues
• dart format — no changes needed

Closes #2662

[wesbillman]

The underlying fix is needed, but this leaves existing invite-created communities only partially repaired. RelayConfig.wsUrl makes their socket connect correctly and queryRelay now converts to HTTP, but mediaUploadServiceProvider still passes config.baseUrl directly to MediaUploadService. For an already-stored wss://... community, _buildUploadRequest therefore still constructs a wss://.../upload URI for package:http, so uploads remain broken. The new normalization only applies to future invite joins; it does not rewrite the records that triggered #2662. Please either migrate/canonicalize existing stored community URLs, or consistently use config.httpUrl at every HTTP consumer (at minimum mediaUploadServiceProvider; audit the remaining config.baseUrl uses). Add coverage for an existing wss:// community exercising the HTTP endpoint derivation.

Separately, DCO is currently failing because the commit lacks the required sign-off.

[alvinjaison]

@wesbillman Addressed your feedback in the force-push:

• mediaUploadServiceProvider and mediaGetAuthServiceProvider now use config.httpUrl
• Added _migrateRelaySchemes in CommunityStorage.loadAll() — rewrites existing stored wss:///ws:// to https:///http:// on first load (persisted)
• Audited remaining config.baseUrl uses — settings_page (display label) and observer_subscription (cache key) are non-HTTP, left as-is
• Added test coverage for the migration + HTTP derivation from a stored wss:// community
• DCO sign-off added

48 tests pass, flutter analyze clean, dart format clean. Ready for re-review.