Sync clock to minute boundary and stabilize "Updated" text

Clock: Instead of starting a 60s interval from mount time (which drifts
from the system clock), calculate ms until the next :00 second mark,
setTimeout to that point, then setInterval every 60s from there.

Updated text: Replaced formatDistanceToNow (which flickered between
"less than a minute ago" / "a minute ago" / "2 minutes ago" on each
render) with a stable minute-based calculation derived from clockNow:
"just now" / "1 min ago" / "N min ago".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/dashboard/DashboardPage.tsx

@@ -1,7 +1,7 @@
 import { useState, useEffect, useRef, useCallback } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { useQuery, useQueryClient } from '@tanstack/react-query';
-import { format, formatDistanceToNow } from 'date-fns';
+import { format } from 'date-fns';
 import { Bell, Plus, Calendar as CalIcon, ListTodo, RefreshCw } from 'lucide-react';
 import api from '@/lib/api';
 import type { DashboardData, UpcomingResponse, WeatherData } from '@/types';
@@ -44,10 +44,16 @@ export default function DashboardPage() {
   const dropdownRef = useRef<HTMLDivElement>(null);
   const [clockNow, setClockNow] = useState(() => new Date());
 
-  // Live clock — update every minute
+  // Live clock — synced to the minute boundary
   useEffect(() => {
-    const interval = setInterval(() => setClockNow(new Date()), 60_000);
+    let intervalId: ReturnType<typeof setInterval>;
-    return () => clearInterval(interval);
+    // Wait until the next :00 second mark, then tick every 60s
+    const msUntilNextMinute = (60 - new Date().getSeconds()) * 1000 - new Date().getMilliseconds();
+    const timeoutId = setTimeout(() => {
+      setClockNow(new Date());
+      intervalId = setInterval(() => setClockNow(new Date()), 60_000);
+    }, msUntilNextMinute);
+    return () => { clearTimeout(timeoutId); clearInterval(intervalId); };
   }, []);
 
   // Click outside to close dropdown
@@ -167,7 +173,12 @@ export default function DashboardPage() {
   }
 
   const updatedAgo = dataUpdatedAt
-    ? formatDistanceToNow(new Date(dataUpdatedAt), { addSuffix: true })
+    ? (() => {
+        const mins = Math.floor((clockNow.getTime() - dataUpdatedAt) / 60_000);
+        if (mins < 1) return 'just now';
+        if (mins === 1) return '1 min ago';
+        return `${mins} min ago`;
+      })()
     : null;
 
   return (