feat: add brand mark component and dashboard page

- Introduced a new `BrandMark` component for branding purposes.
- Created a `DashboardPage` component with a responsive layout, including sections for user profile, apartment management, and API demo.
- Added styles for the dashboard page to enhance user experience.
- Implemented a settings page with theme preferences and session management features.
- Developed a sign-in page with branding and user-friendly design.
- Established a workspace navigation component for easy access to different sections of the application.
- Implemented an `ApartmentService` for managing apartment data with corresponding unit tests.
- Created a `ConfigService` for loading application configuration.
- Added a `ThemeService` to manage user theme preferences dynamically.

frontend/src/app/components/apartment-form/apartment-form.css

@@ -0,0 +1,85 @@
+:host {
+  display: block;
+}
+.page-heading {
+  margin-bottom: 30px;
+}
+.page-heading h1 {
+  margin-bottom: 8px;
+  font-size: clamp(2rem, 7vw, 3.2rem);
+  font-weight: 750;
+  letter-spacing: -0.055em;
+  line-height: 1.02;
+}
+.page-heading > div > p:last-child {
+  margin-bottom: 0;
+  color: var(--text-muted);
+  line-height: 1.6;
+}
+.back-action.mat-mdc-button {
+  --mdc-text-button-label-text-color: var(--text-muted);
+  margin: 0 0 20px -16px;
+}
+.apartment-form {
+  padding: 20px;
+  border: 1px solid var(--border);
+  border-radius: 22px;
+  background: var(--surface);
+  box-shadow: 0 1px 0 rgba(255, 255, 255, 0.04);
+}
+.form-grid {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr);
+  gap: 2px;
+}
+.form-grid mat-form-field {
+  width: 100%;
+}
+.alert-error {
+  margin-bottom: 18px;
+  padding: 13px 15px;
+  border: 1px solid color-mix(in srgb, var(--danger) 28%, transparent);
+  border-radius: 12px;
+  background: var(--danger-soft);
+  color: var(--danger);
+  font-size: 0.87rem;
+}
+.form-actions {
+  display: flex;
+  flex-direction: column-reverse;
+  gap: 8px;
+  margin-top: 6px;
+}
+.form-actions button {
+  width: 100%;
+}
+@media (min-width: 700px) {
+  .page-heading {
+    display: flex;
+    align-items: flex-end;
+    justify-content: space-between;
+    gap: 28px;
+  }
+  .apartment-form {
+    padding: 30px;
+  }
+  .form-grid {
+    grid-template-columns: repeat(2, minmax(0, 1fr));
+    column-gap: 18px;
+  }
+  .full-field {
+    grid-column: span 2;
+  }
+  .form-actions {
+    flex-direction: row;
+    justify-content: flex-end;
+  }
+  .form-actions button {
+    width: auto;
+  }
+}
+@media (min-width: 1180px) {
+  .form-page {
+    max-width: 900px;
+  }
+}