feat(project-editor): finish field descriptions + enum dropdowns across all sections

Wires up the remaining editor sections (theme, header, footer, homepage,
widgets, features, languages, navigation) with the description text and
dropdown UX started for General/Branding:

- Every enum-backed field is now a <select> with a description per option,
  not free text: theme.mode, the new site-wide layout.type (previously had
  no editor at all - added to the Theme section, and added to that
  section's reset-scope), homepage section layout.strategy, and
  catalog.navigationMode (also previously unedited, added to Features).
- Every other field (colors, header toggles, footer contact/company fields,
  widget props, feature flags, language add, nav link label/url/visible)
  gets a one-line plain-language description under its label via the new
  *Desc i18n keys (en/ru/hy) prepared earlier.
- Genuinely open text (widget layout variant strings, JSON props) stays
  free text, description-only, per the existing widgetLayoutDesc/widgetJsonDesc
  wording - not force-fit into a dropdown.

Verified: tsc --noEmit and ng build both clean.

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

@@ -6,9 +6,26 @@
       <div class="sortable-item" cdkDrag>
         <div class="editor-grid four compact">
           <strong>{{ section.id }}</strong>
-          <label><span>{{ 'builder.visible' | translate }}</span><input type="checkbox" [checked]="section.visible !== false" (change)="updateSection(section.id, 'visible', $any($event.target).checked)" /></label>
-          <label><span>{{ 'builder.layoutLabel' | translate }}</span><input type="text" [ngModel]="section.layout?.strategy || ''" (ngModelChange)="updateLayout(section.id, 'strategy', $event)" /></label>
-          <label><span>{{ 'builder.columns' | translate }}</span><input type="number" [ngModel]="section.layout?.columns || 1" (ngModelChange)="updateLayout(section.id, 'columns', $event)" /></label>
+          <label>
+            <span>{{ 'builder.visible' | translate }}</span>
+            <input type="checkbox" [checked]="section.visible !== false" (change)="updateSection(section.id, 'visible', $any($event.target).checked)" />
+            <small class="field-desc">{{ 'builder.sectionVisibleDesc' | translate }}</small>
+          </label>
+          <label>
+            <span>{{ 'builder.layoutStrategyLabel' | translate }}</span>
+            <small class="field-desc">{{ 'builder.layoutStrategyDesc' | translate }}</small>
+            <select [ngModel]="section.layout?.strategy || 'stack'" (ngModelChange)="updateLayout(section.id, 'strategy', $event)">
+              @for (option of layoutStrategyOptions; track option.value) {
+                <option [value]="option.value">{{ option.labelKey | translate }}</option>
+              }
+            </select>
+            <small class="field-desc">{{ layoutStrategyDescKey(section.layout?.strategy || 'stack') | translate }}</small>
+          </label>
+          <label>
+            <span>{{ 'builder.columns' | translate }}</span>
+            <small class="field-desc">{{ 'builder.sectionColumnsDesc' | translate }}</small>
+            <input type="number" [ngModel]="section.layout?.columns || 1" (ngModelChange)="updateLayout(section.id, 'columns', $event)" />
+          </label>
         </div>
       </div>
     }