refactor(logging): reduce download log spam and set INFO level

- Pass app logger to yt-dlp so internal [download] progress lines
  are routed through the INFO-level logger instead of stdout.
- Throttle download_progress_handler debug logging to avoid
  flooding logs on every fragment tick.
- Switch key provider lifecycle messages to INFO (start/complete)
  while keeping verbose details at DEBUG.
- Set debug_enabled=False in development config so dev mode
  does not emit extra debug noise.
- Update config docstring example from DEBUG to INFO.

src/server/config/development.py

@@ -215,7 +215,7 @@ class DevelopmentSettings(BaseSettings):
     @property
     def debug_enabled(self) -> bool:
         """Check if debug mode is enabled."""
-        return True
+        return False
 
     @property
     def reload_enabled(self) -> bool: