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.

Makefile

@@ -5,11 +5,8 @@ build:
 	@echo "Building with GoReleaser..."
 	goreleaser build --clean --snapshot --single-target
 	@mkdir -p bin
-	@find dist -name jiggablend -type f -exec cp {} bin/jiggablend \;
-
-# Build web UI
-build-web: clean-web
-	cd web && npm install && npm run build
+	@find dist -name jiggablend -type f -exec cp {} bin/jiggablend.new \;
+	@mv -f bin/jiggablend.new bin/jiggablend
 
 # Cleanup manager logs
 cleanup-manager:
@@ -63,7 +60,7 @@ clean-bin:
 
 # Clean web build artifacts
 clean-web:
-	rm -rf web/dist/
+	@echo "No generated web artifacts to clean."
 
 # Run tests
 test:
@@ -75,7 +72,7 @@ help:
 	@echo ""
 	@echo "Build targets:"
 	@echo "  build            - Build jiggablend binary with embedded web UI"
-	@echo "  build-web        - Build web UI only"
+	@echo "  build-web        - Validate web UI assets (no build required)"
 	@echo ""
 	@echo "Run targets:"
 	@echo "  run              - Run manager and runner in parallel (for testing)"
@@ -90,7 +87,7 @@ help:
 	@echo ""
 	@echo "Other targets:"
 	@echo "  clean-bin        - Clean build artifacts"
-	@echo "  clean-web        - Clean web build artifacts"
+	@echo "  clean-web        - Clean generated web artifacts (currently none)"
 	@echo "  test             - Run Go tests"
 	@echo "  help             - Show this help"
 	@echo ""