feat: add app edit page with pre-populated form

Add /apps/[id]/edit route that loads existing app data into the form,
allowing users to update app properties. Adds edit pencil button to
AppCard (visible on hover) and i18n keys for both EN and RU.

src/lib/i18n/en.json

@@ -333,6 +333,10 @@
 	"settings.bookmarklet_drag_hint": "Drag this to your bookmarks bar",
 	"settings.bookmarklet_show_code": "Show bookmarklet code",
 
+	"app.edit": "Edit",
+	"app.edit_title": "Edit App",
+	"app.update": "Update App",
+
 	"app.quick_add_title": "Quick Add App",
 	"app.quick_add_description": "Review the details below and save to add this app to your launcher.",
 	"app.quick_add_success": "App added successfully!",