fix(media-picker): reset shared filter state on open instead of eager unconditional load

MediaLibraryFacade is a root-provided singleton shared by every
app-media-picker instance on a page (branding alone renders 4; static-pages
with N pages renders 2N). ngOnInit called facade.load() unconditionally on
mount regardless of whether the dialog was ever opened, and search/folder/
page filters set in one dialog leaked into whichever picker instance was
opened next, since they all read/write the same signals.

Replaced ngOnInit with an effect() that resets search/folder/page and loads
only when this instance's own  input becomes true. Verified live:
searched in one field's picker, closed it, opened a different field's
picker on the same page - search is now reset to empty (previously it
would've carried over 'leftover-search-term').

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

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

@@ -1,4 +1,4 @@
-import { ChangeDetectionStrategy, Component, ElementRef, OnInit, ViewChild, inject, input, output } from '@angular/core';
+import { ChangeDetectionStrategy, Component, ElementRef, ViewChild, effect, inject, input, output } from '@angular/core';
 import { FormsModule } from '@angular/forms';
 import { TranslatePipe } from '../../../i18n/translate.pipe';
 import { MediaLibraryFacade } from '../../../features/backoffice/media/facade/media-library.facade';
@@ -31,7 +31,7 @@ const PAGE_SIZE = 24;
   styleUrl: './media-picker.component.scss',
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
-export class MediaPickerComponent implements OnInit {
+export class MediaPickerComponent {
   readonly open = input(false);
 
   readonly selected = output<MediaAsset>();
@@ -43,9 +43,24 @@ export class MediaPickerComponent implements OnInit {
 
   protected readonly totalPages = () => Math.max(1, Math.ceil(this.facade.total() / PAGE_SIZE));
 
-  ngOnInit(): void {
+  constructor() {
+    // MediaLibraryFacade is a root-provided singleton shared by every
+    // app-media-picker instance on the page (a form with several image
+    // fields renders one instance each). Loading unconditionally in
+    // ngOnInit meant every instance fetched on mount regardless of whether
+    // its dialog was ever opened, and search/folder/page state from one
+    // dialog leaked into whichever picker was opened next. Reset the
+    // shared filters and (re)load only when this instance's dialog
+    // actually opens.
+    effect(() => {
+      if (this.open()) {
+        this.facade.search.set('');
+        this.facade.folder.set(null);
+        this.facade.page.set(1);
         void this.facade.load();
       }
+    });
+  }
 
   protected triggerFileInput(): void {
     this.fileInput?.nativeElement.click();