Refactor application structure to use WorkspaceService for state management

- Removed direct state management from components and centralized it in WorkspaceService.
- Updated ApartmentsPage, TenantsPage, LeasesPage, and DashboardPage to utilize WorkspaceService for data handling.
- Introduced SessionService to manage user session state and authentication.
- Simplified component templates to reflect new service-based architecture.
- Removed unused ConfigService and its tests.
- Added lease.html template for lease document generation.
- Created app.routes.spec.ts for route mapping tests.

frontend/src/app/app.html

@@ -1,13 +1,9 @@
-@if (!isLoggedIn) {
+@if (!session.isLoggedIn()) {
   <app-sign-in-page (loginRequested)="login()" />
 } @else {
   <div class="workspace-shell">
     <app-workspace-navigation
-      [activeTab]="activeTab()"
-      [username]="username"
-      [email]="email"
       [userInitial]="userInitial()"
-      (tabSelected)="activeTab.set($event)"
       (logoutRequested)="logout()"
     />
 
@@ -21,53 +17,7 @@
       </header>
 
       <div class="page-container">
-        @if (activeTab() === 'dashboard') {
-          <app-dashboard-page
-            [username]="username"
-            [email]="email"
-            [userInitial]="userInitial()"
-            [apartmentCount]="apartments().length"
-            [helloMessage]="helloMessage()"
-            (apartmentsRequested)="activeTab.set('apartments')"
-            (connectionCheckRequested)="callHelloApi()"
-          />
-        }
-        @if (activeTab() === 'apartments') {
-          <app-apartments-page
-            [apartments]="apartments()"
-            (deleteRequested)="deleteApartment($event)"
-            (apartmentSaved)="saveApartment($event)"
-          />
-        }
-        @if (activeTab() === 'tenants') {
-          <app-tenants-page
-            [tenants]="tenants()"
-            [attachmentError]="tenantAttachmentError()"
-            (tenantSaved)="saveTenant($event)"
-            (deleteRequested)="deleteTenant($event)"
-            (attachmentUploadRequested)="uploadTenantAttachment($event)"
-            (attachmentDownloadRequested)="downloadTenantAttachment($event)"
-          />
-        }
-        @if (activeTab() === 'leases') {
-          <app-leases-page
-            [leases]="leases()"
-            [apartments]="apartments()"
-            [tenants]="tenants()"
-            (leaseSaved)="saveLease($event)"
-            (deleteRequested)="deleteLease($event)"
-            (pdfRequested)="downloadLeasePdf($event)"
-          />
-        }
-        @if (activeTab() === 'settings') {
-          <app-settings-page
-            [username]="username"
-            [email]="email"
-            [themePreference]="themePreference()"
-            (themePreferenceChanged)="themeService.setPreference($event)"
-            (logoutRequested)="logout()"
-          />
-        }
+        <router-outlet />
       </div>
     </main>
   </div>