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.

.gitignore

@@ -43,16 +43,6 @@ runner-secrets-*.json
 jiggablend-storage/
 jiggablend-workspaces/
 
-# Node.js
-web/node_modules/
-web/dist/
-web/.vite/
-npm-debug.log*
-yarn-debug.log*
-yarn-error.log*
-pnpm-debug.log*
-lerna-debug.log*
-
 # IDE
 .vscode/
 .idea/