fix(backend): Use tenant_id claim name in MCP API Key authentication

Fixed TenantId claim name mismatch between McpApiKeyAuthenticationHandler
and ITenantContext implementations. Changed claim name from "TenantId" to
"tenant_id" to match what TenantContext.GetCurrentTenantId() expects.

This fixes the "TenantId cannot be empty" error when MCP SDK Resources
attempt to retrieve the tenant ID after API Key authentication.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

colaflow-api/src/Modules/Mcp/ColaFlow.Modules.Mcp.Infrastructure/Authentication/McpApiKeyAuthenticationHandler.cs

@@ -48,11 +48,12 @@ public class McpApiKeyAuthenticationHandler : AuthenticationHandler<McpApiKeyAut
         }
 
         // Create claims from validation result
+        // Note: Use "tenant_id" to match ITenantContext implementations that look for this claim name
         var claims = new List<Claim>
         {
             new(ClaimTypes.NameIdentifier, validationResult.UserId.ToString()),
             new("ApiKeyId", validationResult.ApiKeyId.ToString()),
-            new("TenantId", validationResult.TenantId.ToString()),
+            new("tenant_id", validationResult.TenantId.ToString()),
             new("UserId", validationResult.UserId.ToString()),
         };