feat: add YouTube cookies upload via web UI

Adds a Settings panel to upload a cookies.txt file directly from the
browser, persisted in a named Docker volume. yt-dlp uses the file
when present to bypass YouTube bot detection.

docker-compose.yml

@@ -3,8 +3,13 @@ services:
     build: .
     environment:
       - MAX_UPLOAD_SIZE_MB=500
+      - YT_DLP_COOKIES_FILE=/data/yt-cookies.txt
     volumes:
       - /tmp/apoena-audio:/tmp/apoena-audio
+      - apoena-data:/data
+
+volumes:
+  apoena-data:
     labels:
       - 'traefik.http.middlewares.myauth.basicauth.users=julien:$$2y$$05$$1AWK6NyxNNnAX4opcBftnutdMEPTH422uKkNs/NoB3S8i9Bze4GSS'
       - 'traefik.http.routers.http-0-p10gcndwy2krf8zu7swn3i2w-app.middlewares=myauth'