Add Linker and Optimizer modules with API integration and frontend components

- Added Linker and Optimizer apps to `INSTALLED_APPS` in `settings.py`.
- Configured API endpoints for Linker and Optimizer in `urls.py`.
- Implemented `OptimizeContentFunction` for content optimization in the AI module.
- Created prompts for content optimization and site structure generation.
- Updated `OptimizerService` to utilize the new AI function for content optimization.
- Developed frontend components including dashboards and content lists for Linker and Optimizer.
- Integrated new routes and sidebar navigation for Linker and Optimizer in the frontend.
- Enhanced content management with source and sync status filters in the Writer module.
- Comprehensive test coverage added for new features and components.

frontend/src/pages/Linker/__tests__/Dashboard.test.tsx

@@ -0,0 +1,82 @@
+/**
+ * Tests for Linker Dashboard
+ */
+import { render, screen, waitFor } from '@testing-library/react';
+import { BrowserRouter } from 'react-router';
+import LinkerDashboard from '../Dashboard';
+import { fetchContent } from '../../../services/api';
+
+vi.mock('../../../services/api');
+vi.mock('../../../store/siteStore', () => ({
+  useSiteStore: () => ({ activeSite: { id: 1, name: 'Test Site' } }),
+}));
+vi.mock('../../../store/sectorStore', () => ({
+  useSectorStore: () => ({ activeSector: { id: 1, name: 'Test Sector' } }),
+}));
+
+describe('LinkerDashboard', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('renders dashboard title', () => {
+    (fetchContent as any).mockResolvedValue({ results: [], count: 0 });
+    
+    render(
+      <BrowserRouter>
+        <LinkerDashboard />
+      </BrowserRouter>
+    );
+    
+    expect(screen.getByText('Linker Dashboard')).toBeInTheDocument();
+  });
+
+  it('displays stats cards when data is loaded', async () => {
+    (fetchContent as any).mockResolvedValue({
+      results: [
+        { id: 1, internal_links: [{ id: 1 }] },
+        { id: 2, internal_links: [] },
+      ],
+      count: 2,
+    });
+    
+    render(
+      <BrowserRouter>
+        <LinkerDashboard />
+      </BrowserRouter>
+    );
+    
+    await waitFor(() => {
+      expect(screen.getByText('Total Linked')).toBeInTheDocument();
+      expect(screen.getByText('Total Links')).toBeInTheDocument();
+    });
+  });
+
+  it('shows loading state initially', () => {
+    (fetchContent as any).mockImplementation(() => new Promise(() => {}));
+    
+    render(
+      <BrowserRouter>
+        <LinkerDashboard />
+      </BrowserRouter>
+    );
+    
+    expect(screen.getByText('Loading stats...')).toBeInTheDocument();
+  });
+
+  it('renders quick actions', async () => {
+    (fetchContent as any).mockResolvedValue({ results: [], count: 0 });
+    
+    render(
+      <BrowserRouter>
+        <LinkerDashboard />
+      </BrowserRouter>
+    );
+    
+    await waitFor(() => {
+      expect(screen.getByText('Link Content')).toBeInTheDocument();
+      expect(screen.getByText('View Content')).toBeInTheDocument();
+    });
+  });
+});
+