improve startup logging: version, platform, data dir, db stats

Replace verbose startup messages with a clean summary:
- App version, Python version, OS/arch
- Database path (fix None display), data directory
- Profile and generation counts
- Backend, GPU, model cache path
- Clean up stale loading_model status on startup
- Remove noisy progress manager log line

backend/config.py

@@ -4,20 +4,24 @@ Configuration module for voicebox backend.
 Handles data directory configuration for production bundling.
 """
 
+import logging
 import os
 from pathlib import Path
 
+logger = logging.getLogger(__name__)
+
 # Allow users to override the HuggingFace model download directory.
 # Set VOICEBOX_MODELS_DIR to an absolute path before starting the server.
 # This sets HF_HUB_CACHE so all huggingface_hub downloads go to that path.
 _custom_models_dir = os.environ.get("VOICEBOX_MODELS_DIR")
 if _custom_models_dir:
     os.environ["HF_HUB_CACHE"] = _custom_models_dir
-    print(f"[config] Model download path set to: {_custom_models_dir}")
+    logger.info("Model download path set to: %s", _custom_models_dir)
 
 # Default data directory (used in development)
 _data_dir = Path("data")
 
+
 def set_data_dir(path: str | Path):
     """
     Set the data directory path.
@@ -28,7 +32,8 @@ def set_data_dir(path: str | Path):
     global _data_dir
     _data_dir = Path(path)
     _data_dir.mkdir(parents=True, exist_ok=True)
-    print(f"Data directory set to: {_data_dir.absolute()}")
+    logger.info("Data directory set to: %s", _data_dir.absolute())
+
 
 def get_data_dir() -> Path:
     """
@@ -39,28 +44,33 @@ def get_data_dir() -> Path:
     """
     return _data_dir
 
+
 def get_db_path() -> Path:
     """Get database file path."""
     return _data_dir / "voicebox.db"
 
+
 def get_profiles_dir() -> Path:
     """Get profiles directory path."""
     path = _data_dir / "profiles"
     path.mkdir(parents=True, exist_ok=True)
     return path
 
+
 def get_generations_dir() -> Path:
     """Get generations directory path."""
     path = _data_dir / "generations"
     path.mkdir(parents=True, exist_ok=True)
     return path
 
+
 def get_cache_dir() -> Path:
     """Get cache directory path."""
     path = _data_dir / "cache"
     path.mkdir(parents=True, exist_ok=True)
     return path
 
+
 def get_models_dir() -> Path:
     """Get models directory path."""
     path = _data_dir / "models"