polish on archive import processing

dockerfile

@@ -3,10 +3,14 @@ FROM python:slim
 
 WORKDIR /app
 
-# Only what you actually need (ffmpeg kept for video/thumbs)
-RUN apt-get update && \
-    apt-get install -y --no-install-recommends ffmpeg && \
-    rm -rf /var/lib/apt/lists/*
+# System deps for archives and video thumbs (all FOSS)
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    p7zip-full \
+    unar \
+    file \
+    ffmpeg \
+ && rm -rf /var/lib/apt/lists/*
+
 
 # Install deps first for better layer caching
 COPY requirements.txt .