Refactor web build process and update documentation

- Removed Node.js build artifacts from .gitignore and adjusted Makefile to reflect changes in web UI build process, now using server-rendered Go templates instead of React.
- Updated README to clarify the new web UI architecture and output formats, emphasizing the removal of the Node.js build step.
- Added a command to set the number of frames per render task in manager configuration, enhancing user control over rendering settings.
- Improved Gitea workflow by removing unnecessary npm install step, streamlining the CI process.

.goreleaser.yaml

@@ -3,7 +3,6 @@ version: 2
 before:
   hooks:
     - go mod tidy -v
-    - sh -c "cd web && npm install && npm run build"
 
 builds:
   - id: default