Fix prod build: download progress, robust stderr, full tracebacks

- Force tqdm disable=False in TrackedTqdm so byte progress works in prod
  (huggingface_hub disables tqdm based on logger level, which prevents
  self.n from updating — our progress tracking needs the counter even
  though we don't render to terminal)
- Harden devnull redirect to test writability, not just None check
- Add full traceback logging to all backend error handlers
- Add chatterbox/luxtts/zipvoice hidden imports and metadata to spec

backend/backends/chatterbox_turbo_backend.py

@@ -228,7 +228,8 @@ class ChatterboxTurboTTSBackend:
                 task_manager.error_download(model_name, str(e))
             raise
         except Exception as e:
-            logger.error(f"Failed to load Chatterbox Turbo: {e}")
+            import traceback
+            logger.error(f"Failed to load Chatterbox Turbo: {e}\n{traceback.format_exc()}")
             if not is_cached:
                 progress_manager.mark_error(model_name, str(e))
                 task_manager.error_download(model_name, str(e))