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/.dockerignore

@@ -0,0 +1,26 @@
+# Dependencies and build output
+node_modules
+dist
+
+# Git and env
+.git
+.gitignore
+.env*
+!.env.example
+
+# IDE, OS, logs
+.idea
+.vscode
+*.log
+.DS_Store
+
+# Tests (keep image small)
+**/__tests__
+**/*.test.ts
+**/*.test.tsx
+**/*.spec.ts
+**/*.spec.tsx
+coverage
+
+# Dev Dockerfile not needed in prod image
+Dockerfile.dev