feat(project-editor): add field descriptions to General and Branding sections (partial)

Adds a short plain-language description under each field label (new
.field-desc style, section.shared.scss) so a non-developer admin
understands what each field affects, per i18n (en/ru/hy) convention.

Only General and Branding sections are wired up so far - the *Desc i18n
keys for the remaining sections (theme/header/footer/homepage/widgets/
features/languages/navigation) were prepared in translations.ts/en/ru/hy
but not yet wired into their templates. Follow-up work.

src/app/i18n/translations.ts

@@ -529,6 +529,107 @@ export interface Translations {
     resetSection: string;
     confirmResetDraft: string;
     confirmResetSection: string;
+    marketplaceNameDesc: string;
+    domainDesc: string;
+    descriptionFieldDesc: string;
+    defaultLanguageDesc: string;
+    supportedLanguagesDesc: string;
+    logoDesc: string;
+    smallLogoDesc: string;
+    faviconDesc: string;
+    marketplaceTitleDesc: string;
+    primaryColorDesc: string;
+    secondaryColorDesc: string;
+    backgroundColorDesc: string;
+    surfaceColorDesc: string;
+    textColorDesc: string;
+    successColorDesc: string;
+    warningColorDesc: string;
+    dangerColorDesc: string;
+    themeModeLabel: string;
+    themeModeDesc: string;
+    themeModeLight: string;
+    themeModeLightDesc: string;
+    themeModeDark: string;
+    themeModeDarkDesc: string;
+    themeModeSystem: string;
+    themeModeSystemDesc: string;
+    siteLayoutLabel: string;
+    siteLayoutDesc: string;
+    siteLayoutDefault: string;
+    siteLayoutDefaultDesc: string;
+    siteLayoutSidebarLeft: string;
+    siteLayoutSidebarLeftDesc: string;
+    siteLayoutCarouselHome: string;
+    siteLayoutCarouselHomeDesc: string;
+    siteLayoutMinimal: string;
+    siteLayoutMinimalDesc: string;
+    showLogoDesc: string;
+    showSearchDesc: string;
+    showCategoriesDesc: string;
+    showLanguagesDesc: string;
+    showCartDesc: string;
+    showProfileDesc: string;
+    showWishlistDesc: string;
+    showCompareDesc: string;
+    showRegionDesc: string;
+    companyNameDesc: string;
+    addressDesc: string;
+    phoneDesc: string;
+    emailDesc: string;
+    copyrightDesc: string;
+    paymentIconsDesc: string;
+    socialLinksDesc: string;
+    staticPagesFieldDesc: string;
+    sectionVisibleDesc: string;
+    layoutStrategyLabel: string;
+    layoutStrategyDesc: string;
+    layoutStrategyStack: string;
+    layoutStrategyStackDesc: string;
+    layoutStrategyGrid: string;
+    layoutStrategyGridDesc: string;
+    layoutStrategyHero: string;
+    layoutStrategyHeroDesc: string;
+    layoutStrategyCarousel: string;
+    layoutStrategyCarouselDesc: string;
+    layoutStrategySplit: string;
+    layoutStrategySplitDesc: string;
+    sectionColumnsDesc: string;
+    widgetLayoutDesc: string;
+    widgetHeightDesc: string;
+    widgetOverlayDesc: string;
+    widgetAutoplayDesc: string;
+    widgetColumnsDesc: string;
+    widgetCardsPerRowDesc: string;
+    widgetFiltersDesc: string;
+    widgetShowBadgesDesc: string;
+    widgetShowRatingDesc: string;
+    widgetShowPriceDesc: string;
+    widgetJsonDesc: string;
+    wishlistFeatureDesc: string;
+    compareFeatureDesc: string;
+    reviewsFeatureDesc: string;
+    questionsFeatureDesc: string;
+    commentsFeatureDesc: string;
+    recommendationsFeatureDesc: string;
+    recentlyViewedFeatureDesc: string;
+    searchSuggestionsDesc: string;
+    searchHistoryDesc: string;
+    catalogNavigationModeLabel: string;
+    catalogNavigationModeDesc: string;
+    catalogNavDefault: string;
+    catalogNavDefaultDesc: string;
+    catalogNavLeftCategory: string;
+    catalogNavLeftCategoryDesc: string;
+    catalogNavMegaCategory: string;
+    catalogNavMegaCategoryDesc: string;
+    catalogNavTopCarousel: string;
+    catalogNavTopCarouselDesc: string;
+    newLanguageDesc: string;
+    languagesTabDesc: string;
+    linkLabelDesc: string;
+    linkUrlDesc: string;
+    linkVisibleDesc: string;
   };
   dashboard: {
     title: string;