add Podman Quadlet deployment

- flaskpaste.container for rootless systemd integration
- UserNS mapping for bind mount permissions
- README updated with deployment instructions

README.md

@@ -338,6 +338,39 @@ podman run -d -p 5000:5000 -v flaskpaste-data:/app/data flaskpaste
 
 See `Containerfile` for container build configuration.
 
+### Using Podman Quadlet
+
+Quadlet integrates rootless containers with systemd. Deploy as a dedicated user:
+
+```bash
+# Create service user and data directory
+useradd -r -m -d /home/flaskpaste -s /sbin/nologin flaskpaste
+mkdir -p /opt/flaskpaste
+chown flaskpaste:flaskpaste /opt/flaskpaste
+
+# Build image as flaskpaste user
+sudo -u flaskpaste podman build -t localhost/flaskpaste:latest .
+
+# Install Quadlet unit
+mkdir -p /home/flaskpaste/.config/containers/systemd
+cp flaskpaste.container /home/flaskpaste/.config/containers/systemd/
+chown -R flaskpaste:flaskpaste /home/flaskpaste/.config
+
+# Enable lingering (start user services at boot)
+loginctl enable-linger flaskpaste
+
+# Start service
+systemctl --user -M flaskpaste@ daemon-reload
+systemctl --user -M flaskpaste@ start flaskpaste
+```
+
+Manage with systemctl:
+```bash
+systemctl --user -M flaskpaste@ status flaskpaste
+systemctl --user -M flaskpaste@ restart flaskpaste
+journalctl --user -M flaskpaste@ -u flaskpaste
+```
+
 ### Using systemd
 ```bash
 # Create service user
@@ -391,6 +424,8 @@ flaskpaste/
 ├── run.py               # Development server
 ├── wsgi.py              # Production WSGI entry
 ├── Containerfile        # Podman/Docker build
+├── compose.yaml         # Podman/Docker Compose
+├── flaskpaste.container # Podman Quadlet unit
 └── requirements.txt     # Dependencies
 ```