fix: upgrade yt-dlp to 2025.x to fix YouTube extraction

YouTube regularly breaks older yt-dlp versions. Bumped the minimum version
and added a separate Docker layer for yt-dlp so it can be upgraded without
busting the main pip cache.

Dockerfile

@@ -9,6 +9,8 @@ WORKDIR /app
 
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
+# Install yt-dlp last so it can be bumped independently without busting the cache above
+RUN pip install --no-cache-dir --upgrade "yt-dlp>=2025.1"
 
 COPY app/ ./app/