Cleanup: remove unused code, add CI/CD workflow

- Remove flask-sse, Redis (unused)
- Remove ImageService, file_utils (unused)
- Remove /download-posters route (frontend handles download client-side)
- Remove LETTERBOXD_API_URL, secure_filename (dead imports)
- Fix duplicate TMDBService instantiation
- Simplify config.py (remove REDIS_URL)
- Fix gunicorn user home dir for control socket
- Add .gitignore for __pycache__
- Add .gitea/workflows/deploy.yml for tag-based CI/CD

.gitea/workflows/deploy.yml

@@ -0,0 +1,33 @@
+name: Deploy Backend
+
+on:
+  push:
+    tags:
+      - 'v*.*.*'
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Extract version tag
+        run: echo "VERSION_TAG=${GITHUB_REF_NAME}" >> $GITHUB_ENV
+
+      - name: Build Docker image
+        run: |
+          docker build \
+            -t poster-picker-backend:latest \
+            -t poster-picker-backend:${{ env.VERSION_TAG }} .
+
+      - name: Stop old container
+        run: |
+          cd ~/dev-server/poster-picker
+          docker compose stop backend || true
+
+      - name: Start new container
+        run: |
+          cd ~/dev-server/poster-picker
+          docker compose up -d --no-build backend