EM upcoming alert: Arabic copy tweaks (#346)

Two small Arabic-only string changes in the Upcoming Meeting alert
popup, requested off a screenshot:

1. Header title: "اجتماع يبدأ قريبًا" → "الاجتماع التالي".
2. Countdown line: replaced "خلال" with "بعد" so the alert reads
   "يبدأ بعد 5 دقائق" instead of "يبدأ خلال 5 دقائق". Applied to all
   plural forms (one/two/few/many/other). minutesAway_zero ("يبدأ
   الآن") and the separate startsNow key were left unchanged.

Files:
- artifacts/tx-os/src/locales/ar.json
  - executiveMeetings.alert.title
  - executiveMeetings.alert.minutesAway_{one,two,few,many,other}

Out of scope (untouched on purpose):
- en.json — user only asked about the Arabic copy.
- upcoming-meeting-alert.tsx — no logic/layout change needed; it
  already reads these keys via i18next.
- All other behavior (blink, drag, buttons, etc.) carried over from
  #344.

Verification:
- ar.json still valid JSON; key set unchanged.
- Pre-existing red workflows (api-server, combined `test`) are
  unrelated upstream failures and not caused by this change.

artifacts/tx-os/src/locales/ar.json

@@ -1053,13 +1053,13 @@
       }
     },
     "alert": {
-      "title": "اجتماع يبدأ قريبًا",
+      "title": "الاجتماع التالي",
       "minutesAway_zero": "يبدأ الآن",
-      "minutesAway_one": "يبدأ خلال دقيقة",
-      "minutesAway_two": "يبدأ خلال دقيقتين",
-      "minutesAway_few": "يبدأ خلال {{count}} دقائق",
-      "minutesAway_many": "يبدأ خلال {{count}} دقيقة",
-      "minutesAway_other": "يبدأ خلال {{count}} دقيقة",
+      "minutesAway_one": "يبدأ بعد دقيقة",
+      "minutesAway_two": "يبدأ بعد دقيقتين",
+      "minutesAway_few": "يبدأ بعد {{count}} دقائق",
+      "minutesAway_many": "يبدأ بعد {{count}} دقيقة",
+      "minutesAway_other": "يبدأ بعد {{count}} دقيقة",
       "startsNow": "يبدأ الآن",
       "atTime": "في {{time}}",
       "done": "تم",