chore: remove confirmed dead code

Dead code sweep verified manually against app.routes.ts, DI registries, and
cross-repo grep for every candidate (per prior false-positive incident with
knip on pages/**). Deleted only what has zero reachable reference:

Auth (unregistered, comment-only mention):
- core/auth/guards/ed25519-auth.guard.ts - ed25519AuthGuard never imported;
  only mentioned inside a doc-comment in admin-login-page.component.ts.
- core/auth/guards/permission.guard.ts - permissionGuard never imported.
- core/auth/interceptors/auth.interceptor.ts - authInterceptor not present
  in app.config.ts's withInterceptors([...]) list; not imported elsewhere.

Search feature:
- features/search/services/search-analytics.service.ts - SearchAnalyticsService
  never imported outside its own file.
- features/search/components/empty-results/* - app-search-empty-results
  selector never used in any template; search-bar.component.html implements
  its own inline @if (noResults) empty state instead.

Content management:
- features/content-management/pages/content-management-page.component.ts -
  thin wrapper around StaticPagesEditorComponent with zero route pointing at
  it in app.routes.ts. The rest of features/content-management/* (facade,
  static-pages-editor, page-editor, etc.) remains: it is used by
  project-editor and stays.

Backoffice CRUD scaffolding (re-verified the UI-COMPOSITION-REVIEW.md claim
independently): app.routes.ts backoffice section only loads
features/admin/{dashboard,products,categories,transactions,orders,customers,
moderation,users,monitoring,analytics} and features/backoffice/media. Grepped
every other backoffice/* folder for cross-references - none found.
- features/backoffice/{categories,customers,inventory,orders,products,settings}
  - each contained only a placeholder .gitkeep from the original scaffold
  commit (b957112); no real components were ever added, so this is not the
  "duplicate implementation" the prior doc described, just unused scaffold
  dirs. Removing corrects that doc's premise.
- features/backoffice/shared/backoffice-coming-soon-page.component.* - only
  consumer would have been those scaffold dirs; unreferenced elsewhere.
- assets/mock/backoffice/{customers,orders}/list.json - mock data with no
  corresponding fetch call; BackofficeDataProvider only exposes
  loadProducts()/loadCategories(), backed by the products/categories mock
  files, which are kept.

Dead shared barrels/models (no importer anywhere in src/app):
- shared/index.ts, shared/models/index.ts, shared/types/index.ts - unused
  re-export barrels.
- shared/models/domain/index.ts + user-preferences.model.ts (whole domain/
  subfolder) - UserPreferences interface has zero consumers.

Storefront pages (pages/public/platform-home.component.ts) - PlatformHomeComponent
has no route in app.routes.ts and is not imported anywhere; distinct from the
pages/category, pages/search, pages/info/**, pages/legal/**, pages/item-detail
components which ARE routed and were correctly left untouched.

Verification: npx tsc --noEmit -p tsconfig.app.json clean after each batch;
npm run build succeeded (pre-existing initial-bundle-budget warning only,
unrelated to this change).

src/app/features/backoffice/shared/backoffice-coming-soon-page.component.html

@@ -1,5 +0,0 @@
-<div class="coming-soon">
-  <h1 class="coming-soon__title">{{ titleKey | translate }}</h1>
-  <p class="coming-soon__description">{{ 'dashboard.comingSoonDescription' | translate }}</p>
-  <a class="coming-soon__link" [routerLink]="['../dashboard']">{{ 'dashboard.backToDashboard' | translate }}</a>
-</div>

src/app/features/backoffice/shared/backoffice-coming-soon-page.component.scss

@@ -1,32 +0,0 @@
-.coming-soon {
-  display: flex;
-  flex-direction: column;
-  align-items: flex-start;
-  gap: 12px;
-  max-width: 640px;
-  margin: 40px auto;
-  padding: 24px;
-  text-align: left;
-}
-
-.coming-soon__title {
-  margin: 0;
-  font-size: var(--font-size-3xl, 1.5rem);
-  font-weight: 800;
-  color: var(--text-primary, #1e3c38);
-}
-
-.coming-soon__description {
-  margin: 0;
-  color: var(--text-secondary, #667a77);
-}
-
-.coming-soon__link {
-  color: var(--primary-color, #497671);
-  font-weight: var(--font-weight-semibold, 600);
-  text-decoration: none;
-}
-
-.coming-soon__link:hover {
-  text-decoration: underline;
-}

src/app/features/backoffice/shared/backoffice-coming-soon-page.component.ts

@@ -1,19 +0,0 @@
-import { ChangeDetectionStrategy, Component, inject } from '@angular/core';
-import { CommonModule } from '@angular/common';
-import { ActivatedRoute, RouterLink } from '@angular/router';
-import { TranslatePipe } from '../../../i18n/translate.pipe';
-
-/** Landing page for backoffice sections not built yet (categories, static pages, transactions, orders, media). Route `data.titleKey` sets the section name; falls back to the generic "coming soon" title. */
-@Component({
-  selector: 'app-backoffice-coming-soon-page',
-  standalone: true,
-  imports: [CommonModule, RouterLink, TranslatePipe],
-  templateUrl: './backoffice-coming-soon-page.component.html',
-  styleUrls: ['./backoffice-coming-soon-page.component.scss'],
-  changeDetection: ChangeDetectionStrategy.OnPush,
-})
-export class BackofficeComingSoonPageComponent {
-  private readonly route = inject(ActivatedRoute);
-
-  readonly titleKey: string = this.route.snapshot.data['titleKey'] ?? 'dashboard.comingSoonTitle';
-}