feat: add optional YouTube proxy support for IP blocks

Route transcript fetching through YOUTUBE_PROXY or Webshare residential
config, with clearer errors when YouTube still blocks requests.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/settings.py

@@ -18,5 +18,13 @@ class Settings(BaseSettings):
     app_url: str = "http://localhost:8000"
     app_version: str = "1.0.0"
 
+    # YouTube transcript proxy (optional — for IP blocks)
+    # Single URL used for HTTP+HTTPS, e.g. http://user:pass@host:port
+    youtube_proxy: str = ""
+    # Webshare rotating residential (paid package — NOT free "Proxy Server" tier)
+    webshare_proxy_username: str = ""
+    webshare_proxy_password: str = ""
+    webshare_proxy_locations: str = ""  # comma-separated, e.g. de,es
+
 
 settings = Settings()  # type: ignore[call-arg]