feat(seo): tenant-driven meta tags, sitemap/robots, reduced-motion, docs

Completes the rest of Sprint 28 on top of the earlier admin-scoped
a11y/skeleton pass (576f260):

- SeoService.resetToDefaults() now reads real bootstrap.seo.default /
  branding instead of hardcoded placeholder text + a broken
  /og-image.jpg reference; auto-reapplies via an effect() whenever
  bootstrap (re)loads, same pattern as UiRuntimeFacade.
- New public/sitemap.xml (static baseline, documented per-tenant-dynamic
  limitation) + public/robots.txt Sitemap directive and admin/editor
  Disallow rules.
- Global prefers-reduced-motion override in styles.scss covering every
  existing hover-transform/fade-in/shimmer animation in one place.
- New adminProducts/adminUsers/adminMonitoring/adminAnalytics
  empty-state i18n keys (en/ru/hy) for this sprint's skeleton/empty-state
  consistency fixes.
- docs/KNOWN-ISSUES.md: logged a newly-found, much larger pre-existing
  gap (~178 missing adminXxx.* i18n keys across the whole admin
  backoffice) - deferred to Sprint 29's translation validation, not
  fixed here.
- docs/BACKEND.md: new item 17 (sitemap generation gap).
- docs/ADMIN.md, docs/SPRINT-PLAN.md: rewritten Sprint 28 sections to
  describe the full, combined scope (both commits) instead of the
  earlier admin-only framing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/i18n/en.ts

@@ -862,4 +862,21 @@ export const en: Translations = {
     emptyTitle: 'No files yet',
     emptyDescription: 'Upload an image or document to get started.',
   },
+  adminProducts: {
+    emptyTitle: 'No products found',
+    emptyDescription: 'Try adjusting your filters, or create a new product.',
+  },
+  adminUsers: {
+    emptyTitle: 'No users found',
+    emptyDescription: 'Invite a teammate to get started.',
+    invitationsEmptyTitle: 'No pending invitations',
+  },
+  adminMonitoring: {
+    eventsEmptyTitle: 'No events found',
+    eventsEmptyDescription: 'Try a different category filter or search term.',
+  },
+  adminAnalytics: {
+    topProductsEmptyTitle: 'No product sales in this period',
+    topProductsEmptyDescription: 'Try a wider date range.',
+  },
 };

src/app/i18n/hy.ts

@@ -857,4 +857,21 @@ export const hy: Translations = {
     emptyTitle: 'Ֆայլեր դեռ չկան',
     emptyDescription: 'Վերբեռնեք պատկեր կամ փաստաթուղթ սկսելու համար։',
   },
+  adminProducts: {
+    emptyTitle: 'Ապրանքներ չեն գտնվել',
+    emptyDescription: 'Փոխեք ֆիլտրերը կամ ստեղծեք նոր ապրանք։',
+  },
+  adminUsers: {
+    emptyTitle: 'Օգտատերեր չեն գտնվել',
+    emptyDescription: 'Հրավիրեք գործընկերոջ՝ սկսելու համար։',
+    invitationsEmptyTitle: 'Սպասող հրավերներ չկան',
+  },
+  adminMonitoring: {
+    eventsEmptyTitle: 'Իրադարձություններ չեն գտնվել',
+    eventsEmptyDescription: 'Փորձեք այլ կատեգորիայի ֆիլտր կամ որոնման բառ։',
+  },
+  adminAnalytics: {
+    topProductsEmptyTitle: 'Այս ժամանակահատվածում ապրանքների վաճառք չկա',
+    topProductsEmptyDescription: 'Փորձեք ընտրել ավելի լայն ամսաթվերի միջակայք։',
+  },
 };

src/app/i18n/ru.ts

@@ -857,4 +857,21 @@ export const ru: Translations = {
     emptyTitle: 'Пока нет файлов',
     emptyDescription: 'Загрузите изображение или документ, чтобы начать.',
   },
+  adminProducts: {
+    emptyTitle: 'Товары не найдены',
+    emptyDescription: 'Измените фильтры или создайте новый товар.',
+  },
+  adminUsers: {
+    emptyTitle: 'Пользователи не найдены',
+    emptyDescription: 'Пригласите коллегу, чтобы начать.',
+    invitationsEmptyTitle: 'Нет ожидающих приглашений',
+  },
+  adminMonitoring: {
+    eventsEmptyTitle: 'События не найдены',
+    eventsEmptyDescription: 'Попробуйте изменить фильтр категории или поисковый запрос.',
+  },
+  adminAnalytics: {
+    topProductsEmptyTitle: 'Нет продаж товаров за этот период',
+    topProductsEmptyDescription: 'Попробуйте выбрать более широкий диапазон дат.',
+  },
 };

src/app/i18n/translations.ts

@@ -860,4 +860,25 @@ export interface Translations {
     emptyTitle: string;
     emptyDescription: string;
   };
+  // Sprint 28: only the new empty-state copy this sprint's skeleton/empty-
+  // state consistency fix introduces - NOT the full adminProducts/
+  // adminUsers/adminMonitoring/adminAnalytics translation surface, which is
+  // still missing entirely (see docs/KNOWN-ISSUES.md, deferred to Sprint 29).
+  adminProducts: {
+    emptyTitle: string;
+    emptyDescription: string;
+  };
+  adminUsers: {
+    emptyTitle: string;
+    emptyDescription: string;
+    invitationsEmptyTitle: string;
+  };
+  adminMonitoring: {
+    eventsEmptyTitle: string;
+    eventsEmptyDescription: string;
+  };
+  adminAnalytics: {
+    topProductsEmptyTitle: string;
+    topProductsEmptyDescription: string;
+  };
 }

src/app/services/seo.service.ts

@@ -1,8 +1,9 @@
-import { Injectable, inject, DOCUMENT } from '@angular/core';
+import { Injectable, inject, DOCUMENT, effect } from '@angular/core';
 import { Meta, Title } from '@angular/platform-browser';
 import { Item } from '../models';
 import { getDiscountedPrice, getMainImage } from '../utils/item.utils';
 import { UiRuntimeFacade } from '../facades/runtime/ui-runtime.facade';
+import { ConfigService } from '../core/config/config.service';
 
 @Injectable({
   providedIn: 'root'
@@ -12,6 +13,22 @@ export class SeoService {
   private title = inject(Title);
   private doc = inject(DOCUMENT);
   private readonly uiRuntime = inject(UiRuntimeFacade);
+  private readonly configService = inject(ConfigService);
+
+  constructor() {
+    // Keep the runtime <title>/OG/Twitter/canonical/robots tags in sync with
+    // the tenant's own bootstrap.seo.default + branding config whenever it
+    // (re)loads - the static defaults in index.html are only a pre-JS /
+    // no-JS-crawler fallback and are otherwise stuck on the hardcoded
+    // "Marketplace" placeholder tenant. Item-detail pages override these via
+    // setItemMeta() and restore them via resetToDefaults() on navigating away.
+    effect(() => {
+      this.configService.bootstrapRevision();
+      if (this.configService.getBootstrapSnapshot()) {
+        this.resetToDefaults();
+      }
+    });
+  }
 
   private get siteUrl(): string {
     return this.doc?.location?.origin ?? '';
@@ -60,14 +77,32 @@ export class SeoService {
   }
 
   /**
-   * Reset meta tags back to defaults (call on navigation away from item page).
+   * Reset meta tags back to the tenant's own site-wide defaults (call on
+   * navigation away from an item page, and also applied automatically
+   * whenever the bootstrap config (re)loads - see constructor).
+   *
+   * Reads `bootstrap.seo.default` (title/description/canonicalUrl/robots/
+   * metaTags - editable in the Project Editor's General/Branding sections,
+   * previously authored but never actually applied anywhere) and
+   * `bootstrap.branding` (name/logo, for the OG/Twitter image) so the runtime
+   * tags reflect the real tenant instead of a hardcoded "Marketplace"
+   * placeholder. Falls back to generic copy only if bootstrap hasn't loaded
+   * yet or a field is unset.
    */
   resetToDefaults(): void {
-    const defaultTitle = `${this.siteName} — Marketplace`;
-    const defaultDescription = 'Modern marketplace for buying digital goods. Wide selection, convenient search, fast delivery.';
-    const defaultImage = `${this.siteUrl}/og-image.jpg`;
+    const bootstrap = this.configService.getBootstrapSnapshot();
+    const seoDefault = bootstrap?.seo?.default;
+    const branding = bootstrap?.branding;
+
+    const defaultTitle = seoDefault?.title || `${this.siteName} — Marketplace`;
+    const defaultDescription = seoDefault?.description
+      || 'Modern marketplace for buying digital goods. Wide selection, convenient search, fast delivery.';
+    const defaultImage = this.resolveUrl(branding?.appIconUrl || branding?.logoUrl || '')
+      || `${this.siteUrl}/icons/icon-512x512.png`;
+    const canonicalUrl = seoDefault?.canonicalUrl ? this.resolveUrl(seoDefault.canonicalUrl) : this.siteUrl;
 
     this.title.setTitle(defaultTitle);
+    this.setCanonical(canonicalUrl);
 
     this.setOrUpdate([
       { property: 'og:type', content: 'website' },
@@ -84,12 +119,14 @@ export class SeoService {
       { name: 'twitter:image', content: defaultImage },
 
       { name: 'description', content: defaultDescription },
+
+      ...(seoDefault?.robots ? [{ name: 'robots', content: seoDefault.robots }] : []),
+      ...(seoDefault?.metaTags ?? []),
     ]);
 
     // Remove product-specific tags
     this.meta.removeTag("property='product:price:amount'");
     this.meta.removeTag("property='product:price:currency'");
-    this.removeCanonical();
   }
 
   private setOrUpdate(tags: Array<{ property?: string; name?: string; content: string }>): void {