fix: Properly handle HTTPException in signals endpoint

- Added specific exception handling for HTTPException to prevent double-wrapping
- HTTPException instances are now re-raised directly without modification
- This ensures clear error messages are returned to the client

src/dashboard/api.py

@@ -649,6 +649,9 @@ async def get_signals():
                         status_code=503,
                         detail="No signals available from protocol servers. Please check server connectivity."
                     )
+            except HTTPException:
+                # Re-raise HTTP exceptions directly
+                raise
             except Exception as e:
                 logger.error("failed_to_get_protocol_data", error=str(e))
                 raise HTTPException(