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.

internal/manager/blender.go

@@ -331,8 +331,9 @@ func (s *Manager) GetBlenderArchivePath(version *BlenderVersion) (string, error)
 	// Need to download and decompress
 	log.Printf("Downloading Blender %s from %s", version.Full, version.URL)
 
+	// 60-minute timeout for large Blender tarballs; stream to disk via io.Copy below
 	client := &http.Client{
-		Timeout: 0, // No timeout for large downloads
+		Timeout: 60 * time.Minute,
 	}
 	resp, err := client.Get(version.URL)
 	if err != nil {