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/ChairTool.ts

@@ -0,0 +1,58 @@
+import { Tool } from '../Tool';
+import { YjsDocument } from '../../crdt/YjsDocument';
+
+class ChairTool extends Tool {
+  private width: number = 45; // Default chair width
+  private height: number = 45; // Default chair height
+
+  constructor(yjsDoc: YjsDocument) {
+    super(yjsDoc);
+    this.name = 'ChairTool';
+  }
+
+  onMouseDown(event: MouseEvent): void {
+    // Create chair element at click position
+    const x = event.clientX - this.width / 2;
+    const y = event.clientY - this.height / 2;
+    
+    this.yjsDoc.createElement({
+      id: crypto.randomUUID(),
+      type: 'chair',
+      layerId: 'default',
+      x,
+      y,
+      width: this.width,
+      height: this.height,
+      properties: {
+        // Chair-specific properties can be added here
+      }
+    });
+  }
+
+  onMouseMove(event: MouseEvent): void {
+    // Preview chair at cursor position
+  }
+
+  onMouseUp(event: MouseEvent): void {
+    // Handle mouse up if needed
+  }
+
+  onKeyUp(event: KeyboardEvent): void {
+    // Handle key up events
+    if (event.key === 'Escape') {
+      this.reset();
+    }
+  }
+
+  reset(): void {
+    // Reset any state if needed
+  }
+
+  // Set chair dimensions
+  setDimensions(width: number, height: number): void {
+    this.width = width;
+    this.height = height;
+  }
+}
+
+export { ChairTool };