feat(project-editor): per-field inline validation for languages, homepage, widgets, navigation, static-pages

Extends the fieldError() wiring pattern (already used in theme/general/branding)
to the remaining sections that have matching ProjectValidator fieldKeys:
- languages: localization.supportedLocales (no-languages, missing-translations)
- homepage: pages (empty-homepage, missing-widget, duplicate-routes)
- widgets: pages (invalid-widget-config)
- navigation: navigation.header (duplicate-nav-links)
- static-pages: staticPages (duplicate-slugs, invalid-css)

Header/footer/features sections have no matching validator issues today,
so nothing to wire there yet.

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

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

@@ -3,6 +3,7 @@ import { ChangeDetectionStrategy, Component, computed, inject } from '@angular/c
 import { FormsModule } from '@angular/forms';
 import { ProjectEditorFacade } from '../facade/project-editor.facade';
 import { TranslatePipe } from '../../../i18n/translate.pipe';
+import { TranslateService } from '../../../i18n/translate.service';
 import { InputComponent } from '../../../shared/ui/input/input.component';
 import { SectionCardComponent } from '../../../shared/ui/section-card/section-card.component';
 import { ToggleComponent } from '../../../shared/ui/toggle/toggle.component';
@@ -23,7 +24,12 @@ export interface LayoutStrategyOption {
 })
 export class ProjectEditorHomepageSectionComponent {
   private readonly facade = inject(ProjectEditorFacade);
+  private readonly translate = inject(TranslateService);
   readonly homePage = this.facade.homepagePage;
+  readonly fieldError = (key: string): string | null => {
+    const messageKey = this.facade.fieldError(key);
+    return messageKey ? this.translate.t(messageKey) : null;
+  };
   readonly sections = computed(() => [...(this.homePage()?.sections ?? [])].sort((a, b) => a.order - b.order));
 
   readonly layoutStrategyOptions: LayoutStrategyOption[] = [