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/runner/encoding/encoder.go

@@ -20,10 +20,8 @@ type EncodeConfig struct {
 	StartFrame   int     // Starting frame number
 	FrameRate    float64 // Frame rate
 	WorkDir      string  // Working directory
-	UseAlpha     bool    // Whether to preserve alpha channel
-	TwoPass      bool    // Whether to use 2-pass encoding
-	SourceFormat string  // Source format: "exr" or "png" (defaults to "exr")
-	PreserveHDR  bool    // Whether to preserve HDR range for EXR (uses HLG with bt709 primaries)
+	UseAlpha bool   // Whether to preserve alpha channel
+	TwoPass  bool   // Whether to use 2-pass encoding
 }
 
 // Selector selects the software encoder.