Add category filtering, default to copy mode, split dev/prod compose

- Default MOVE_MODE changed to copy so qBit can continue seeding
- Add QBIT_CATEGORY env var (default "Stash") to filter torrents
- Split compose into dev (build from source) and prod (pre-built image)
- Fix Dockerfile COPY glob needing trailing slash
- Update README and summary docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -2,6 +2,6 @@ FROM python:3.12-slim
 WORKDIR /app
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
-COPY *.py .
+COPY *.py ./
 ENTRYPOINT ["python", "stash_handler.py"]
 CMD ["daemon"]