refactor(shared): modality-scoped tool categories, dissolve ai category

Replace the flat 12-category structure with 27 modality-scoped
sub-categories. The cross-modality "ai" category is dissolved: each
AI tool moves into its natural modality's sub-category (e.g.
remove-background -> image/enhance, auto-subtitles -> video/subtitles,
ocr -> documents/convert, transcribe-audio -> audio/convert).

New category hierarchy:
- Image (8): essentials, adjustments, enhance, watermark, layout,
  utilities, optimization, format
- Video (5): video-edit, video-convert, video-effects,
  video-subtitles, video-metadata
- Audio (4): audio-edit, audio-convert, audio-effects, audio-metadata
- Documents (5): pdf-organize, pdf-edit, pdf-security, pdf-optimize,
  doc-convert
- Data (2): data, archives

No tool IDs, routes, or backend behavior changed. Category labels
updated across all 21 locales.

packages/shared/src/i18n/ar.ts

@@ -41,17 +41,29 @@ export const ar: TranslationKeys = {
   },
   categories: {
     essentials: "الأساسيات",
-    optimization: "التحسين",
     adjustments: "التعديلات",
+    enhance: "Enhance & AI",
     watermark: "العلامة المائية والتراكب",
-    utilities: "الأدوات المساعدة",
     layout: "التخطيط والتكوين",
+    utilities: "الأدوات المساعدة",
+    optimization: "التحسين",
     format: "التنسيق والتحويل",
-    video: "Video",
-    audio: "Audio",
-    documents: "PDF & Documents",
+    "video-edit": "Video",
+    "video-convert": "Convert",
+    "video-effects": "Effects & Compose",
+    "video-subtitles": "Subtitles",
+    "video-metadata": "Metadata",
+    "audio-edit": "Edit",
+    "audio-convert": "Convert",
+    "audio-effects": "Effects & Compose",
+    "audio-metadata": "Metadata",
+    "pdf-organize": "Organize",
+    "pdf-edit": "Edit & Annotate",
+    "pdf-security": "Security",
+    "pdf-optimize": "Optimize",
+    "doc-convert": "Convert",
     data: "Data Files",
-    ai: "أدوات AI",
+    archives: "Archives",
   },
   modalities: {
     image: "Image",