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-api/pom.xml

@@ -123,6 +123,11 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-actuator</artifactId>
         </dependency>
+        <!-- WebSocket (STOMP + SockJS for notifications) -->
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-websocket</artifactId>
+        </dependency>
     </dependencies>
 
     <build>

cannamanage-api/src/main/java/de/cannamanage/api/config/WebSocketConfig.java

@@ -0,0 +1,34 @@
+package de.cannamanage.api.config;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.messaging.simp.config.MessageBrokerRegistry;
+import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
+import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
+import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;
+
+/**
+ * WebSocket configuration — enables STOMP messaging over SockJS.
+ * Clients connect to /ws, subscribe to /user/queue/notifications for personal notifications.
+ */
+@Configuration
+@EnableWebSocketMessageBroker
+public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
+
+    @Override
+    public void configureMessageBroker(MessageBrokerRegistry config) {
+        // Enable simple in-memory broker for /topic (broadcast) and /queue (user-specific)
+        config.enableSimpleBroker("/topic", "/queue");
+        // Prefix for @MessageMapping methods
+        config.setApplicationDestinationPrefixes("/app");
+        // User-specific destination prefix
+        config.setUserDestinationPrefix("/user");
+    }
+
+    @Override
+    public void registerStompEndpoints(StompEndpointRegistry registry) {
+        // WebSocket endpoint with SockJS fallback
+        registry.addEndpoint("/ws")
+                .setAllowedOriginPatterns("*")
+                .withSockJS();
+    }
+}

cannamanage-api/src/main/java/de/cannamanage/api/controller/NotificationController.java

@@ -0,0 +1,68 @@
+package de.cannamanage.api.controller;
+
+import de.cannamanage.domain.entity.Notification;
+import de.cannamanage.service.NotificationService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.security.core.annotation.AuthenticationPrincipal;
+import org.springframework.security.core.userdetails.UserDetails;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+/**
+ * REST endpoints for notification management.
+ */
+@RestController
+@RequestMapping("/api/v1/notifications")
+@RequiredArgsConstructor
+public class NotificationController {
+
+    private final NotificationService notificationService;
+
+    /**
+     * Get current user's notifications (last 10, unread first).
+     */
+    @GetMapping
+    public ResponseEntity<Map<String, Object>> getNotifications(@AuthenticationPrincipal UserDetails user) {
+        UUID userId = UUID.fromString(user.getUsername());
+        List<Notification> notifications = notificationService.getRecentNotifications(userId);
+        long unreadCount = notificationService.getUnreadCount(userId);
+
+        var items = notifications.stream().map(n -> Map.of(
+                "id", (Object) n.getId(),
+                "type", n.getType().name(),
+                "title", n.getTitle(),
+                "message", n.getMessage(),
+                "link", n.getLink() != null ? n.getLink() : "",
+                "read", n.isRead(),
+                "createdAt", n.getCreatedAt().toString()
+        )).toList();
+
+        return ResponseEntity.ok(Map.of(
+                "notifications", items,
+                "unreadCount", unreadCount
+        ));
+    }
+
+    /**
+     * Mark a single notification as read.
+     */
+    @PutMapping("/{id}/read")
+    public ResponseEntity<Void> markAsRead(@PathVariable UUID id) {
+        notificationService.markAsRead(id);
+        return ResponseEntity.noContent().build();
+    }
+
+    /**
+     * Mark all notifications as read.
+     */
+    @PutMapping("/read-all")
+    public ResponseEntity<Map<String, Object>> markAllAsRead(@AuthenticationPrincipal UserDetails user) {
+        UUID userId = UUID.fromString(user.getUsername());
+        int updated = notificationService.markAllAsRead(userId);
+        return ResponseEntity.ok(Map.of("updated", updated));
+    }
+}

cannamanage-api/src/main/resources/db/migration/V10__notifications.sql

@@ -0,0 +1,15 @@
+-- V10: Notifications table for real-time + persistent notification system
+CREATE TABLE IF NOT EXISTS notifications (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id UUID NOT NULL,
+    type VARCHAR(50) NOT NULL,
+    title VARCHAR(255) NOT NULL,
+    message TEXT NOT NULL,
+    link VARCHAR(500),
+    read BOOLEAN NOT NULL DEFAULT false,
+    created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT NOW(),
+    tenant_id UUID NOT NULL
+);
+
+CREATE INDEX idx_notifications_user ON notifications(user_id, read, created_at DESC);
+CREATE INDEX idx_notifications_tenant ON notifications(tenant_id);