feat(coming-soon): premium themed redesign with launch countdown

Full refactor of the maintenance/coming-soon page for all locales (de/en/ar,
RTL-aware) with a refined, theme-aware (light + dark) premium composition:
glass panel, live status indicator, hero title, description, launch countdown
and CTAs. Reuses the existing hero/motion system; no new dependencies.

- Add components/site/launch-countdown.tsx: hydration-safe client countdown
  (days/hours/minutes/seconds), localized labels, Arabic-aware typography,
  "launched" fallback when the target passes.
- Rewrite app/[locale]/coming-soon/page.tsx around the countdown and a single
  easy-to-edit LAUNCH_DATE_ISO constant (default ~45 days out).
- Add comingSoon i18n keys (status, countdownLabel, unit labels, launched)
  to en/de/ar.

messages/en.json

@@ -28,7 +28,14 @@
     "titleLineThree": "returning soon",
     "description": "I am rebuilding the site to present services, selected work, and collaboration details with sharper structure and less noise.",
     "primaryCta": "Start a project",
-    "secondaryCta": "Back to homepage"
+    "secondaryCta": "Back to homepage",
+    "status": "In development · back soon",
+    "countdownLabel": "Launching in",
+    "unitDays": "Days",
+    "unitHours": "Hours",
+    "unitMinutes": "Minutes",
+    "unitSeconds": "Seconds",
+    "launched": "Launching very soon"
   },
   "homepage": {
     "meta": {