feat(dashboard): Notifications & sound settings panel (fa/en/ar)

New Settings → "Notifications & sound" leaf to make the alert channels
changeable: toggle sound (+ picker with live preview + volume slider),
enable desktop notifications (permission flow + test button), toggle the
tab unread badge and in-app toasts. Strings added for fa/en/ar.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/dashboard/messages/en.json

@@ -1272,6 +1272,7 @@
       "shop": "Shop & café",
       "shopGeneral": "Profile & integrations",
       "shopAppearance": "Appearance & colors",
+      "shopNotifications": "Notifications & sound",
       "printer": "Printer",
       "printerSettings": "Printer settings",
       "printTest": "Print test page",
@@ -1279,6 +1280,39 @@
       "team": "Team & Staff",
       "customRoles": "Custom Roles"
     },
+    "notifPrefs": {
+      "soundSection": "Sound",
+      "soundEnabled": "Play a sound for new notifications",
+      "soundEnabledHint": "Chimes when a new order, waiter call, or alert arrives.",
+      "soundChoice": "Notification sound",
+      "preview": "Preview",
+      "volume": "Volume",
+      "soundClassic": "Classic",
+      "soundDing": "Ding",
+      "soundBell": "Bell",
+      "soundChime": "Chime",
+      "soundMarimba": "Marimba",
+      "soundAlert": "Alert",
+      "desktopSection": "Desktop notifications",
+      "desktopHint": "Show a Windows/desktop popup even when the dashboard is in another tab or minimized.",
+      "enableDesktop": "Enable desktop notifications",
+      "desktopEnabled": "Desktop popups",
+      "desktopEnabledHint": "Pop up only when this tab is not focused.",
+      "desktopGranted": "Desktop notifications enabled",
+      "desktopDenied": "Permission denied by the browser",
+      "desktopBlocked": "Notifications are blocked for this site. Allow them in your browser's site settings, then reload.",
+      "desktopUnsupported": "This browser does not support desktop notifications.",
+      "desktopFocusNote": "A test popup only appears if you switch to another window first.",
+      "sendTest": "Send a test notification",
+      "testTitle": "Meezi",
+      "testBody": "This is a test notification.",
+      "testToast": "Test sent",
+      "inAppSection": "In-app",
+      "tabBadge": "Unread count on the browser tab",
+      "tabBadgeHint": "Shows the number of unread notifications in the tab title and favicon.",
+      "toast": "In-app toast",
+      "toastHint": "Show a small banner inside the dashboard for new notifications."
+    },
     "customRoles": {
       "title": "Custom Roles",
       "subtitle": "Define roles with tailored permissions for your staff",