feat: home nudge for existing users with no phone number

Existing users (signed up before phone collection) won't have a number.
Show a dismissable home banner prompting them to add one.

- Checks /api/auth/profile on load; shows banner only if user.phone is empty
- "Add" links to /profile; ✕ dismisses
- Dismissal remembered in localStorage (tia_phone_nudge_dismissed) so it
  never nags repeatedly
- Dark-mode styled, sits below the vaccine reminder banner

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

src/app/(app)/home/page.tsx

@@ -99,6 +99,7 @@ export default function HomePage() {
   const [recentLogs, setRecentLogs] = useState<Log[]>([]);
   const [logsLoading, setLogsLoading] = useState(true);
   const [vaccineReminders, setVaccineReminders] = useState<any[]>([]);
+  const [showPhoneNudge, setShowPhoneNudge] = useState(false);
   const [aiChips, setAiChips] = useState<string[]>([]);
   const [uploadingPhoto, setUploadingPhoto] = useState(false);
   const [photoError, setPhotoError]         = useState(false);
@@ -134,6 +135,24 @@ export default function HomePage() {
     return () => window.removeEventListener("online", handleOnline);
   }, [childId]);
 
+  // One-time nudge for existing users who have no phone number on file.
+  // Dismissable; remembered in localStorage so it never nags repeatedly.
+  useEffect(() => {
+    if (!childId) return;
+    if (localStorage.getItem("tia_phone_nudge_dismissed") === "1") return;
+    fetch("/api/auth/profile")
+      .then(r => r.json())
+      .then(data => {
+        if (data.user && !data.user.phone) setShowPhoneNudge(true);
+      })
+      .catch(() => {});
+  }, [childId]);
+
+  const dismissPhoneNudge = () => {
+    setShowPhoneNudge(false);
+    localStorage.setItem("tia_phone_nudge_dismissed", "1");
+  };
+
   const fetchRecentLogs = async () => {
     if (!childId) return;
     try {
@@ -413,6 +432,29 @@ export default function HomePage() {
         </div>
       )}
 
+      {showPhoneNudge && (
+        <div className="mx-4 mb-4 bg-rose-50 dark:bg-rose-900/20 border border-rose-200 dark:border-rose-800/40 px-4 py-3 rounded-xl flex items-center gap-3">
+          <span className="text-xl flex-shrink-0">📱</span>
+          <div className="flex-1 min-w-0">
+            <div className="font-semibold text-rose-700 dark:text-rose-300 text-sm">Add your phone number</div>
+            <div className="text-xs text-rose-600 dark:text-rose-400">Get important reminders &amp; updates about your baby</div>
+          </div>
+          <Link
+            href="/profile"
+            className="flex-shrink-0 text-xs font-semibold text-white bg-rose-400 px-3 py-1.5 rounded-lg active:scale-95 transition-transform"
+          >
+            Add
+          </Link>
+          <button
+            onClick={dismissPhoneNudge}
+            className="flex-shrink-0 text-rose-300 dark:text-rose-500 text-lg leading-none px-1"
+            aria-label="Dismiss"
+          >
+            ✕
+          </button>
+        </div>
+      )}
+
       <TodaySummary logs={recentLogs} />
 
       {stage && (() => {