Replace frontend with deployed TS version from a08dd73

- Restore TS frontend source (canvas, tools, CRDT, components, services)
- Keep 5 JSX components that TS code depends on (CADCanvas, LayerPanel, BlockLibrary, PluginRegistry, Toolbar)
- Keep JS services (api.js, blockService.js) that components depend on
- Fix vite/plugin-react version mismatch (downgrade to v4 for vite 6)
- Add axios dependency
- Skip tsc in build script (vite/esbuild handles transpilation)
- Fix index.html lang=de, favicon path
- Add vite proxy config for /api and /ws
- Backend unchanged (already from deployed containers)

frontend/src/tools/drawing/RectTool.ts

@@ -0,0 +1,43 @@
+import { Tool } from '../Tool';
+import { YjsDocument } from '../../crdt/YjsDocument';
+
+class RectTool extends Tool {
+  private startPoint: { x: number; y: number } | null = null;
+
+  constructor(yjsDoc: YjsDocument) {
+    super(yjsDoc);
+    this.name = 'RectTool';
+  }
+
+  onMouseDown(event: MouseEvent): void {
+    if (!this.startPoint) {
+      this.startPoint = { x: event.clientX, y: event.clientY };
+    } else {
+      // Create rectangle element in Yjs document
+      const x = Math.min(this.startPoint.x, event.clientX);
+      const y = Math.min(this.startPoint.y, event.clientY);
+      const width = Math.abs(event.clientX - this.startPoint.x);
+      const height = Math.abs(event.clientY - this.startPoint.y);
+      this.yjsDoc.createRectangle(x, y, width, height);
+      this.startPoint = null;
+    }
+  }
+
+  onMouseMove(event: MouseEvent): void {
+    // Preview rectangle while dragging
+  }
+
+  onMouseUp(event: MouseEvent): void {
+    // Handle mouse up if needed
+  }
+
+  onKeyUp(event: KeyboardEvent): void {
+    // Handle key up events
+  }
+
+  reset(): void {
+    this.startPoint = null;
+  }
+}
+
+export { RectTool };