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/core/providers/enhanced_provider.py

@@ -566,6 +566,7 @@ class EnhancedAniWorldLoader(Loader):
                     "nocheckcertificate": True,
                     "socket_timeout": self.download_timeout,
                     "http_chunk_size": 1024 * 1024,  # 1MB chunks
+                    "logger": self.logger,
                 }
                 if headers:
                     ydl_opts['http_headers'] = headers