fix(builder): composition audit fixes for project editor sections

- Reset-section button: raw <button> with hardcoded colors -> app-button variant="danger"
- section.shared.scss: raw button/input/select colors switched to CSS theme vars (--primary-color, --bg-primary, --bg-secondary, --error-color) instead of bare hex
- save-bar scss referenced nonexistent CSS vars (--surface, --border, --warning, --danger, --muted-foreground, --info-bg, --info) that always fell back to hardcoded hex; renamed to the real theme vars (--bg-primary, --border-color, --warning-color, --error-color, --text-secondary, --info-color) so the save bar is actually theme-aware
- footer/homepage/widgets section scss: nonexistent --danger-color var renamed to --error-color
- static-pages-editor: replaced dead `.editor-section-card` wrapper class (removed from shared stylesheet in the Sprint 30 redesign, never migrated here) with app-section-card, restoring the card chrome every sibling editor section has
- widgets-section: empty state (no widgets) rendered nothing; added app-empty-state
- homepage-section: empty state (no homepage page) rendered nothing; added app-empty-state
- navigation-section: header/footer nav move-up/move-down buttons had no accessible name (bare uarr/darr glyphs); added aria-label
- Added builder.widgetsEmptyTitle/Desc and builder.homepageEmptyTitle/Desc i18n keys (en/ru/hy)

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

src/app/features/project-editor/sections/widgets-section.component.ts

@@ -7,6 +7,7 @@ import { InputComponent } from '../../../shared/ui/input/input.component';
 import { ButtonComponent } from '../../../shared/ui/button/button.component';
 import { SectionCardComponent } from '../../../shared/ui/section-card/section-card.component';
 import { ToggleComponent } from '../../../shared/ui/toggle/toggle.component';
+import { EmptyStateComponent } from '../../../shared/ui/empty-state/empty-state.component';
 import { WidgetConfig } from '../../../shared/models/config';
 import { IconComponent } from '../../../shared/ui/icon/icon.component';
 import { AppIconName } from '../../../shared/ui/icon/icon-registry';
@@ -31,7 +32,7 @@ const WIDGET_LABEL_KEYS: Record<string, string> = {
 @Component({
   selector: 'app-project-editor-widgets-section',
   standalone: true,
-  imports: [FormsModule, TranslatePipe, InputComponent, ButtonComponent, SectionCardComponent, ToggleComponent, IconComponent],
+  imports: [FormsModule, TranslatePipe, InputComponent, ButtonComponent, SectionCardComponent, ToggleComponent, EmptyStateComponent, IconComponent],
   templateUrl: './widgets-section.component.html',
   styleUrls: ['./section.shared.scss', './widgets-section.component.scss'],
   changeDetection: ChangeDetectionStrategy.OnPush