chore(cleanup): Phase 1 - remove dead code, fix orphaned SeoService wiring

Ran knip to find unused exports/dependencies (deps already clean, no
unused packages/files found).

Removed genuinely dead code (verified zero references anywhere,
including templates):
- 4 unused constants in config/constants.ts (scroll/pagination/search
  thresholds never consumed)
- isAdminRole(), toSearchResult(), createInitialSearchState(),
  getTranslatedCategoryName() - unused utility functions
- DEFAULT_EDITOR_HEADER_CONFIG - unused constant
- TelegramService - entire file deleted; cart.component.ts/
  cart.service.ts already implement the same window.Telegram.WebApp
  access directly, this was an unused duplicate

Real bug fix found during the sweep: SeoService has providedIn:'root'
with a live effect() meant to sync <title>/OG/canonical tags to
tenant bootstrap config, but nothing in the app ever injected it, so
Angular never instantiated it and the effect never ran - the SEO sync
a prior sprint reported as "done and verified" was actually dead on
arrival. Fixed by injecting SeoService in the root App component.

Left alone: ~125 knip-flagged "unused exported types" - overwhelmingly
config/schema interfaces for the widget/theme/admin domain models,
high false-positive rate for this kind of interface-heavy Angular app,
deleting blind risks breaking structural type contracts. Also left
locally-used-but-over-exported helpers (toCssColor/toBackendColor,
HTML_EDITOR_TOOLBAR*, HISTORY_LIMIT, DEFAULT_CATALOG_PAGE_SIZE) - real
code, not dead, just exported wider than needed.

tsc --noEmit and ng build --configuration=production both clean (only
pre-existing bundle-budget warning, unrelated).

Files changed: src/app/app.ts, src/app/config/constants.ts,
src/app/core/auth/models/permission.model.ts,
src/app/core/products/models/catalog-experience.model.ts,
src/app/core/search/models/search-state.model.ts,
src/app/features/project-editor/models/project-editor.model.ts,
src/app/services/index.ts, src/app/utils/item.utils.ts,
src/app/services/telegram.service.ts (deleted)

src/app/core/auth/models/permission.model.ts

@@ -28,7 +28,3 @@ export const ROLE_PERMISSIONS: Readonly<Record<AdminRole, readonly Permission[]>
   Support: ['backoffice.read'],
   ReadOnly: ['backoffice.read', 'builder.read']
 };
-
-export function isAdminRole(value: unknown): value is AdminRole {
-  return typeof value === 'string' && value in ROLE_PERMISSIONS;
-}

src/app/core/products/models/catalog-experience.model.ts

@@ -67,20 +67,3 @@ export interface SearchResult {
   pageSize: number;
   summary: string;
 }
-
-export function toSearchResult(result: ProductListResult, criteria: SearchCriteria): SearchResult {
-  const pageSize = Math.max(1, criteria.pageSize ?? result.count ?? 24);
-  const page = Math.max(1, criteria.page ?? Math.floor((result.skip ?? 0) / pageSize) + 1);
-  const keyword = (criteria.keyword ?? '').trim();
-
-  return {
-    criteria,
-    items: result.items,
-    total: result.total,
-    page,
-    pageSize,
-    summary: keyword.length > 0
-      ? `Results for "${keyword}" (${result.total})`
-      : `Products found: ${result.total}`
-  };
-}

src/app/core/search/models/search-state.model.ts

@@ -10,18 +10,3 @@ export interface SearchState {
 	pageSize: number;
 	filters: SearchFilterState;
 }
-
-export function createInitialSearchState(pageSize = 24): SearchState {
-	return {
-		text: '',
-		sort: 'relevance',
-		layout: 'grid',
-		page: 1,
-		pageSize,
-		filters: {
-			values: {},
-			ranges: {},
-			toggles: {},
-		},
-	};
-}