feat(media): add reusable MediaPickerComponent

Standalone dialog (app-dialog, size lg) reusing MediaLibraryFacade so it
shares the exact same asset list/search/pagination/upload state as the
Media Manager page. Emits (selected) with the chosen MediaAsset and
(closed) to dismiss - selecting a tile emits both.

Completes Sprint 4 (Media Manager): ADR-0002 contract, MediaRepository +
mock IndexedDB adapter, Media Manager UI, reusable Media Picker.

Not yet wired into Product Editor or Static Pages editor - that's the
next natural step when those features gain image fields, not part of
this sprint's scope.

src/app/shared/media/media-picker/media-picker.component.html

@@ -0,0 +1,56 @@
+<app-dialog
+  [open]="open()"
+  [titleText]="'mediaLibrary.title' | translate"
+  size="lg"
+  (closed)="requestClose()"
+>
+  <div class="media-picker">
+    <div class="media-picker__toolbar">
+      <app-input
+        [ngModel]="facade.search()"
+        (ngModelChange)="facade.setSearch($event)"
+        [placeholder]="'mediaLibrary.searchPlaceholder' | translate"
+      />
+      <input
+        #fileInput
+        type="file"
+        accept="image/*,application/pdf"
+        hidden
+        (change)="onFileSelected($event)"
+      />
+      <app-button variant="secondary" [loading]="facade.uploading()" (click)="triggerFileInput()">
+        {{ (facade.uploading() ? 'mediaLibrary.uploading' : 'mediaLibrary.upload') | translate }}
+      </app-button>
+    </div>
+
+    @if (facade.loading()) {
+      <div class="media-picker__grid">
+        @for (i of [1, 2, 3, 4]; track i) {
+          <app-skeleton shape="rect" height="110px" />
+        }
+      </div>
+    } @else if (facade.items().length === 0) {
+      <app-empty-state
+        [title]="'mediaLibrary.emptyTitle' | translate"
+        [description]="'mediaLibrary.emptyDescription' | translate"
+      />
+    } @else {
+      <div class="media-picker__grid">
+        @for (asset of facade.items(); track asset.id) {
+          <app-card padding="sm" [interactive]="true" (click)="pick(asset)">
+            @if (asset.mimeType.startsWith('image/')) {
+              <img class="media-picker__preview" [src]="asset.url" [alt]="asset.filename" />
+            } @else {
+              <div class="media-picker__preview media-picker__preview--file">{{ asset.mimeType }}</div>
+            }
+            <span class="media-picker__filename">{{ asset.filename }}</span>
+          </app-card>
+        }
+      </div>
+
+      @if (totalPages() > 1) {
+        <app-pagination [currentPage]="facade.page()" [totalPages]="totalPages()" (pageChange)="facade.setPage($event)" />
+      }
+    }
+  </div>
+</app-dialog>