style(backend): apply dotnet format whitespace normalization

- Applied dotnet format to 24 files in backend/
- Corrects spacing, indentation, and formatting consistency
- No functional changes to code logic

Ultraworked with Sisyphus <https://github.com/code-yeongyu/oh-my-opencode>
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/WorkClub.Infrastructure/Services/TenantProvider.cs

@@ -27,7 +27,7 @@ public class TenantProvider : ITenantProvider
         {
             throw new InvalidOperationException("Tenant context is not available");
         }
-        
+
         return tenantInfo.Identifier;
     }
 
@@ -41,7 +41,7 @@ public class TenantProvider : ITenantProvider
 
         var tenantId = GetTenantId();
         var clubsClaim = httpContext.User.FindFirst("clubs")?.Value;
-        
+
         if (string.IsNullOrEmpty(clubsClaim))
         {
             throw new InvalidOperationException("User does not have clubs claim");