feat(sprint-6): Phase 6 — Notifications (WebSocket) + PWA

- WebSocket: Spring STOMP + SockJS, NotificationService, persistent notifications table
- NotificationController: GET/PUT endpoints for notification management
- Frontend: notification bell with unread badge, dropdown panel, real-time via STOMP
- PWA: manifest.json, service worker (manual sw.js), offline page, install prompt
- PWA icons (192+512), dark theme colors, standalone display
- Full i18n (de/en) for notifications and PWA
- Flyway V10 migration for notifications table
- spring-boot-starter-websocket dependency added

cannamanage-frontend/src/app/layout.tsx

@@ -11,6 +11,8 @@ import type { ReactNode } from "react"
 
 import { Toaster as Sonner } from "@/components/ui/sonner"
 import { Toaster } from "@/components/ui/toaster"
+import { PwaInstallPrompt } from "@/components/pwa-install-prompt"
+import { ServiceWorkerRegistration as SwRegistration } from "@/components/sw-registration"
 
 // Define metadata for the application
 // More info: https://nextjs.org/docs/app/building-your-application/optimizing/metadata
@@ -21,6 +23,13 @@ export const metadata: Metadata = {
   },
   description: "Cannabis club management platform — CannaManage",
   metadataBase: new URL(process.env.BASE_URL as string),
+  manifest: "/manifest.json",
+  themeColor: "#2ECC71",
+  appleWebApp: {
+    capable: true,
+    statusBarStyle: "default",
+    title: "CannaManage",
+  },
 }
 
 // Define fonts for the application
@@ -55,6 +64,8 @@ export default function RootLayout(props: { children: ReactNode }) {
           {children}
           <Toaster />
           <Sonner />
+          <SwRegistration />
+          <PwaInstallPrompt />
         </Providers>
       </body>
     </html>