fix: Comprehensive authentication and UI fixes

Authentication & Token Management:
- Add deviceId to token refresh flow (backend requires both refreshToken and deviceId)
- Fix React Strict Mode token clearing race condition with retry logic
- Improve AuthContext to handle all token state combinations properly
- Store deviceId in localStorage alongside tokens

UI/UX Improvements:
- Remove deprecated legacyBehavior from Next.js Link components
- Update primary theme color to WCAG AA compliant #7c3aed
- Fix nested button error in TabBar voice navigation
- Fix invalid Tabs value error in DynamicChildDashboard

Multi-Child Dashboard:
- Load all children into Redux store properly
- Fetch metrics for all children, not just selected one
- Remove mock data to prevent unauthorized API calls

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-web/components/dashboard/DynamicChildDashboard.tsx

@@ -49,19 +49,25 @@ export default function DynamicChildDashboard({
   const children = useSelector((state: RootState) => childrenSelectors.selectAll(state));
   const viewMode = useSelector(selectViewMode);
   const selectedChild = useSelector(selectSelectedChild);
-  const [selectedTab, setSelectedTab] = useState<string>('');
+
+  // Initialize selectedTab with first available child ID
+  const [selectedTab, setSelectedTab] = useState<string>(() => {
+    if (selectedChild?.id) return selectedChild.id;
+    if (children.length > 0) return children[0].id;
+    return '';
+  });
 
   // Initialize selected tab
   useEffect(() => {
-    if (selectedChild?.id) {
+    if (selectedChild?.id && selectedTab !== selectedChild.id) {
       setSelectedTab(selectedChild.id);
-    } else if (children.length > 0) {
+    } else if (!selectedTab && children.length > 0) {
       const firstChildId = children[0].id;
       setSelectedTab(firstChildId);
       dispatch(selectChild(firstChildId));
       onChildSelect(firstChildId);
     }
-  }, [selectedChild, children, dispatch, onChildSelect]);
+  }, [selectedChild, children, dispatch, onChildSelect, selectedTab]);
 
   const handleTabChange = (_event: React.SyntheticEvent, newValue: string) => {
     setSelectedTab(newValue);
@@ -180,6 +186,11 @@ export default function DynamicChildDashboard({
 
   // Tab view for 1-3 children
   if (viewMode === 'tabs') {
+    // Don't render tabs if no children or no valid selectedTab
+    if (children.length === 0 || !selectedTab) {
+      return null;
+    }
+
     return (
       <Box>
         <Tabs