fix: stabilize auth-to-tenant flow and correct tenant header mapping

Resolve post-login routing and tenant context issues by proxying frontend API
calls, redirecting authenticated users away from /login, and hardening club
loading with retries/loading guards.

Align tenant identity end-to-end by returning tenantId in /api/clubs/me and
sending X-Tenant-Id from cookie-backed tenantId instead of local clubId,
restoring authorized tasks/shifts data access after club selection.

backend/WorkClub.Application/Clubs/DTOs/ClubListDto.cs

@@ -4,4 +4,5 @@ public record ClubListDto(
     Guid Id,
     string Name,
     string SportType,
-    int MemberCount);
+    int MemberCount,
+    Guid TenantId);