feat: add node help system and registry for extensible node types

- Implemented a help system for different node types (config, render, variable, function) with detailed usage instructions.
- Created a node registry to manage node types, including registration, retrieval, and validation of connections between nodes.
- Defined central node and edge types for the application to streamline state management.
- Added Nunjucks autocomplete functionality to enhance user experience in template editing.
- Developed a syntax highlighting parser for PlantUML and Nunjucks within the CodeMirror editor.
- Registered built-in node types at application startup, including their default configurations and help entries.
- Introduced a theme context provider to manage light/dark mode preferences across the application.
- Created utility functions for class name management using clsx and tailwind-merge.
- Set up Tailwind CSS for styling with custom themes and responsive design.
- Configured Vite for development with proxy settings for backend API calls and Kroki diagram service.

frontend/vite.config.ts

@@ -0,0 +1,43 @@
+import { defineConfig } from 'vite'
+import react from '@vitejs/plugin-react'
+import path from 'path'
+
+
+export default defineConfig({
+  plugins: [react()],
+  server: {
+    proxy: {
+      // Backend API (dev): proxy to avoid CORS
+      '/api/todos': {
+        target: 'http://localhost:8080',
+        changeOrigin: true,
+      },
+      '/api/todos/': {
+        target: 'http://localhost:8080',
+        changeOrigin: true,
+      },
+      '/health': {
+        target: 'http://localhost:8080',
+        changeOrigin: true,
+      },
+      // Kroki diagram service
+      '/api/kroki': {
+        target: 'https://kroki.io',
+        changeOrigin: true,
+        rewrite: (path) => path.replace(/^\/api\/kroki/, ''),
+      },
+    },
+  },
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, './src'),
+      // Ensure PostCSS/Vite can resolve the shadcn tailwind CSS file
+      'shadcn/dist/tailwind.css': path.resolve(
+        __dirname,
+        'node_modules/shadcn/dist/tailwind.css'
+      ),
+      // Optional: map the package to its dist for other imports
+      shadcn: path.resolve(__dirname, 'node_modules/shadcn/dist'),
+    }
+  }
+})