feat: Reports & Analytics page, CSV export, notification bell in header

- Reports page with overview stats, client growth chart, email activity chart
- Engagement breakdown (engaged/warm/cooling/cold) with stacked bar
- Industry and tag distribution charts
- At-risk client lists (cold + cooling)
- CSV export button downloads all clients
- Notification bell in top bar: overdue events, upcoming events, stale clients, pending drafts
- Dismissable notifications with priority indicators
- Added Reports to sidebar nav between Network and Settings

src/lib/api.ts

@@ -404,6 +404,49 @@ class ApiClient {
     }
     return response.json();
   }
+  // Reports & Analytics
+  async getReportsOverview(): Promise<any> {
+    return this.fetch('/reports/overview');
+  }
+
+  async getReportsGrowth(): Promise<any> {
+    return this.fetch('/reports/growth');
+  }
+
+  async getReportsIndustries(): Promise<any[]> {
+    return this.fetch('/reports/industries');
+  }
+
+  async getReportsTags(): Promise<any[]> {
+    return this.fetch('/reports/tags');
+  }
+
+  async getReportsEngagement(): Promise<any> {
+    return this.fetch('/reports/engagement');
+  }
+
+  async getNotifications(): Promise<any> {
+    return this.fetch('/reports/notifications');
+  }
+
+  async exportClientsCSV(): Promise<void> {
+    const token = this.getToken();
+    const headers: HeadersInit = token ? { Authorization: `Bearer ${token}` } : {};
+    const response = await fetch(`${API_BASE}/reports/export/clients`, {
+      headers,
+      credentials: 'include',
+    });
+    if (!response.ok) throw new Error('Export failed');
+    const blob = await response.blob();
+    const url = window.URL.createObjectURL(blob);
+    const a = document.createElement('a');
+    a.href = url;
+    a.download = `clients-export-${new Date().toISOString().split('T')[0]}.csv`;
+    document.body.appendChild(a);
+    a.click();
+    document.body.removeChild(a);
+    window.URL.revokeObjectURL(url);
+  }
 }
 
 export const api = new ApiClient();