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/main.py

@@ -15,6 +15,7 @@ from rehearsalhub.routers import (
     annotations_router,
     auth_router,
     bands_router,
+    invites_router,
     internal_router,
     members_router,
     sessions_router,
@@ -71,6 +72,7 @@ def create_app() -> FastAPI:
     prefix = "/api/v1"
     app.include_router(auth_router, prefix=prefix)
     app.include_router(bands_router, prefix=prefix)
+    app.include_router(invites_router, prefix=prefix)
     app.include_router(sessions_router, prefix=prefix)
     app.include_router(songs_router, prefix=prefix)
     app.include_router(versions_router, prefix=prefix)