chore: initial project setup with backend, frontend, and infrastructure

Add complete NexaPantry application structure including:
- Docker Compose configuration with PostgreSQL, Redis, FastAPI backend, worker, frontend and Caddy
- Environment configuration template with database, auth, and service settings
- GitHub Actions CI workflow for backend/frontend linting, testing, auditing and Docker builds
- AGPL-3.0 license and comprehensive README with setup, development, and security documentation
- Backend

frontend/src/pages/ScannerPage.tsx

@@ -0,0 +1,42 @@
+import { BrowserMultiFormatReader } from '@zxing/browser';
+import { ScanLine } from 'lucide-react';
+import { useEffect, useRef, useState } from 'react';
+import { api } from '../api/client';
+import { Panel } from '../components/Forms';
+import { ProductForm } from '../components/ProductForm';
+import { useAuth } from '../contexts/AuthContext';
+import { useI18n } from '../contexts/I18nContext';
+import type { Product } from '../types';
+
+export function ScannerPage() {
+  const videoRef = useRef<HTMLVideoElement | null>(null);
+  const { activeHome } = useAuth();
+  const { t } = useI18n();
+  const [barcode, setBarcode] = useState('');
+  const [prefill, setPrefill] = useState<Partial<Product>>({});
+
+  useEffect(() => {
+    if (!activeHome || !videoRef.current) return;
+    const reader = new BrowserMultiFormatReader();
+    let controls: { stop: () => void } | undefined;
+    let stop = false;
+    reader.decodeFromVideoDevice(undefined, videoRef.current, async (result) => {
+      if (result && !stop) {
+        stop = true;
+        const code = result.getText();
+        setBarcode(code);
+        const lookup = await api<{ found: boolean; product?: Partial<Product> }>(`/homes/${activeHome.id}/products/lookup/${code}`);
+        setPrefill(lookup.product ?? { barcode: code });
+      }
+    }).then((scannerControls) => { controls = scannerControls; }).catch(() => undefined);
+    return () => { stop = true; controls?.stop(); };
+  }, [activeHome]);
+
+  return (
+    <div className="grid gap-4">
+      <h1 className="flex items-center gap-2 text-3xl font-bold"><ScanLine /> {t('scanBarcode')}</h1>
+      <video ref={videoRef} className="aspect-video w-full rounded-lg bg-gray-950 object-cover" muted playsInline />
+      {barcode ? <Panel title={`${t('barcode')}: ${barcode}`}><ProductForm initial={prefill} onSaved={() => setPrefill({})} /></Panel> : null}
+    </div>
+  );
+}