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.

pkg/scripts/scripts/render_blender.py.template

@@ -95,31 +95,20 @@ if current_device:
 print(f"Blend file output format: {current_output_format}")
 
 # Override output format if specified
-# The format file always takes precedence (it's written specifically for this job)
+# Render output is EXR only and must remain linear for the encode pipeline (linear -> sRGB -> HLG).
 if output_format_override:
-    print(f"Overriding output format from '{current_output_format}' to '{output_format_override}'")
-    # Map common format names to Blender's format constants
-    # For video formats, we render as appropriate frame format first
-    format_to_use = output_format_override.upper()
-    if format_to_use in ['EXR_264_MP4', 'EXR_AV1_MP4', 'EXR_VP9_WEBM']:
-        format_to_use = 'EXR'  # Render as EXR for EXR video formats
-    
-    format_map = {
-        'PNG': 'PNG',
-        'JPEG': 'JPEG',
-        'JPG': 'JPEG',
-        'EXR': 'OPEN_EXR',
-        'OPEN_EXR': 'OPEN_EXR',
-        'TARGA': 'TARGA',
-        'TIFF': 'TIFF',
-        'BMP': 'BMP',
-    }
-    blender_format = format_map.get(format_to_use, format_to_use)
+    print(f"Overriding output format from '{current_output_format}' to OPEN_EXR (always EXR for pipeline)")
     try:
-        scene.render.image_settings.file_format = blender_format
-        print(f"Successfully set output format to: {blender_format}")
+        scene.render.image_settings.file_format = 'OPEN_EXR'
+        # Lock output color space to linear (defense in depth; EXR is linear for encode pipeline)
+        if getattr(scene.render.image_settings, 'has_linear_colorspace', False) and hasattr(scene.render.image_settings, 'linear_colorspace_settings'):
+            try:
+                scene.render.image_settings.linear_colorspace_settings.name = 'Linear'
+            except Exception as ex:
+                print(f"Note: Could not set linear output: {ex}")
+        print("Successfully set output format to: OPEN_EXR")
     except Exception as e:
-        print(f"Warning: Could not set output format to {blender_format}: {e}")
+        print(f"Warning: Could not set output format to OPEN_EXR: {e}")
         print(f"Using blend file's format: {current_output_format}")
 else:
     print(f"Using blend file's output format: {current_output_format}")