feat: Add real-time notification center with WebSocket integration

- Add in-app notification system with database storage
- Implement bell icon component with unread count badge in dashboard header
- Add full Notifications page tab with pagination and filtering (All/Unread/Read)
- Implement real-time WebSocket push notifications to all connected clients
- Add notification API endpoints: GET, PUT /read, DELETE, POST /clear
- Fix critical bug in notificationService where 'status' variable was undefined
- Add Notifications route to App.js routing
- Enhanced UI with notification popup in header and dedicated full-page view
- Auto-reconnect WebSocket with 5s timeout on disconnect
- Support rich notification content with resource details and timestamps

server/auditLog.js

@@ -0,0 +1,152 @@
+const db = require('./database');
+
+class AuditLogger {
+  // Log an audit event
+  log(action, entityType, entityId, changes = {}, userId = 'system', ipAddress = null) {
+    try {
+      db.prepare(`
+        INSERT INTO audit_logs 
+        (action, entity_type, entity_id, user_id, changes, ip_address, created_at)
+        VALUES (?, ?, ?, ?, ?, ?, datetime('now'))
+      `).run(
+        action,
+        entityType,
+        entityId,
+        userId,
+        JSON.stringify(changes),
+        ipAddress
+      );
+    } catch (error) {
+      // Silent failure - don't crash on audit logging errors
+    }
+  }
+
+  // Log resource changes
+  logResourceChange(action, resourceId, changes, userId = 'system', ipAddress = null) {
+    this.log(action, 'resource', resourceId, changes, userId, ipAddress);
+  }
+
+  // Log settings changes
+  logSettingsChange(settingKey, oldValue, newValue, userId = 'system', ipAddress = null) {
+    this.log('update', 'settings', settingKey, { old: oldValue, new: newValue }, userId, ipAddress);
+  }
+
+  // Log group changes
+  logGroupChange(action, groupId, changes, userId = 'system', ipAddress = null) {
+    this.log(action, 'group', groupId, changes, userId, ipAddress);
+  }
+
+  // Log maintenance window changes
+  logMaintenanceChange(action, windowId, changes, userId = 'system', ipAddress = null) {
+    this.log(action, 'maintenance_window', windowId, changes, userId, ipAddress);
+  }
+
+  // Get audit logs with filters
+  getAuditLogs(filters = {}) {
+    const {
+      entityType = null,
+      entityId = null,
+      userId = null,
+      action = null,
+      startDate = null,
+      endDate = null,
+      limit = 100,
+      offset = 0
+    } = filters;
+
+    let query = `
+      SELECT 
+        id,
+        action,
+        entity_type,
+        entity_id,
+        user_id,
+        changes,
+        ip_address,
+        REPLACE(created_at, ' ', 'T') || 'Z' as created_at
+      FROM audit_logs
+      WHERE 1=1
+    `;
+    const params = [];
+
+    if (entityType) {
+      query += ' AND entity_type = ?';
+      params.push(entityType);
+    }
+
+    if (entityId) {
+      query += ' AND entity_id = ?';
+      params.push(entityId);
+    }
+
+    if (userId) {
+      query += ' AND user_id = ?';
+      params.push(userId);
+    }
+
+    if (action) {
+      query += ' AND action = ?';
+      params.push(action);
+    }
+
+    if (startDate) {
+      query += ' AND created_at >= ?';
+      params.push(startDate);
+    }
+
+    if (endDate) {
+      query += ' AND created_at <= ?';
+      params.push(endDate);
+    }
+
+    query += ' ORDER BY created_at DESC LIMIT ? OFFSET ?';
+    params.push(limit, offset);
+
+    try {
+      const logs = db.prepare(query).all(...params);
+      
+      // Parse JSON changes
+      return logs.map(log => ({
+        ...log,
+        changes: log.changes ? JSON.parse(log.changes) : {}
+      }));
+    } catch (error) {
+      return [];
+    }
+  }
+
+  // Get audit summary stats
+  getSummary(days = 7) {
+    try {
+      const stats = db.prepare(`
+        SELECT 
+          COUNT(*) as total_events,
+          COUNT(DISTINCT user_id) as unique_users,
+          COUNT(DISTINCT entity_type) as entity_types,
+          action,
+          COUNT(*) as action_count
+        FROM audit_logs
+        WHERE created_at > datetime('now', '-' || ? || ' days')
+        GROUP BY action
+      `).all(days);
+
+      const totalEvents = db.prepare(`
+        SELECT COUNT(*) as count
+        FROM audit_logs
+        WHERE created_at > datetime('now', '-' || ? || ' days')
+      `).get(days);
+
+      return {
+        totalEvents: totalEvents?.count || 0,
+        actionBreakdown: stats.map(s => ({
+          action: s.action,
+          count: s.action_count
+        }))
+      };
+    } catch (error) {
+      return { totalEvents: 0, actionBreakdown: [] };
+    }
+  }
+}
+
+module.exports = new AuditLogger();