Phase 1 backend implementation: Add invite management endpoints

Implements core invite management features for band admins:
- GET /bands/{band_id}/invites - List all invites for a band (admin only)
- DELETE /invites/{invite_id} - Revoke pending invite (admin only)
- GET /invites/{token}/info - Get invite details (public)

Backend changes:
- Add invites router with 3 endpoints
- Update BandRepository with get_invites_for_band and get_invite_by_id methods
- Add new schemas for invite listing and info
- Register invites router in main.py

Tests:
- Integration tests for all 3 endpoints
- Permission tests (admin vs non-admin)
- Edge cases (not found, expired, etc.)

This addresses the core requirements:
- Admins can see pending invites
- Admins can revoke pending invites
- Users can view invite details before accepting

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

api/src/rehearsalhub/routers/__init__.py

@@ -1,6 +1,7 @@
 from rehearsalhub.routers.annotations import router as annotations_router
 from rehearsalhub.routers.auth import router as auth_router
 from rehearsalhub.routers.bands import router as bands_router
+from rehearsalhub.routers.invites import router as invites_router
 from rehearsalhub.routers.internal import router as internal_router
 from rehearsalhub.routers.members import router as members_router
 from rehearsalhub.routers.sessions import router as sessions_router
@@ -11,6 +12,7 @@ from rehearsalhub.routers.ws import router as ws_router
 __all__ = [
     "auth_router",
     "bands_router",
+    "invites_router",
     "internal_router",
     "members_router",
     "sessions_router",