Add automatic Nicotine+ version checking and building

- Workflow checks PyPI hourly for new Nicotine+ versions
- Automatically builds and pushes new images when updates are available
- Creates Gitea releases tagged with Nicotine+ version
- Supports manual trigger and push events

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

README.md

@@ -95,7 +95,16 @@ docker exec -it nicotine-less nicotine
 
 ## Updates
 
-To update Nicotine+ to the latest version, rebuild the container:
+**Automatic updates**: The container image is automatically rebuilt every hour when a new Nicotine+ version is released on PyPI.
+
+To update to the latest version, pull the new image:
+
+```bash
+docker compose pull
+docker compose up -d
+```
+
+Or rebuild locally:
 
 ```bash
 docker compose down
@@ -103,13 +112,6 @@ docker compose build --no-cache
 docker compose up -d
 ```
 
-Or pull the pre-built image from the registry:
-
-```bash
-docker compose pull
-docker compose up -d
-```
-
 ## License
 
 This project is provided "as-is" without warranties.