fix(api): log internal handler errors

Tower-http's TraceLayer logged the failure status code but not the
underlying error, leaving 500s opaque without curling the response
body. Log the error from the internal() helper so server logs carry
the actual cause (permission denied, query error, etc.).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/moments-api/src/main.rs

@@ -145,9 +145,11 @@ impl ApiError {
 }
 
 fn internal<E: std::fmt::Display>(e: E) -> ApiError {
+    let message = e.to_string();
+    tracing::error!(error = %message, "internal handler error");
     ApiError {
         status: StatusCode::INTERNAL_SERVER_ERROR,
-        message: e.to_string(),
+        message,
     }
 }