Add skeleton loading states across all tracking pages

- Replace CircularProgress spinners with content-aware skeleton screens
- Add FormSkeleton for form loading states (feeding, sleep, diaper pages)
- Add ActivityListSkeleton for recent activities loading
- Improves perceived performance with layout-matching placeholders

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

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

maternal-web/app/track/sleep/page.tsx

@@ -24,6 +24,7 @@ import {
   Chip,
   Snackbar,
 } from '@mui/material';
+import { FormSkeleton, ActivityListSkeleton } from '@/components/common/LoadingSkeletons';
 import {
   ArrowBack,
   Refresh,
@@ -320,8 +321,17 @@ export default function SleepTrackPage() {
     return (
       <ProtectedRoute>
         <AppShell>
-          <Box sx={{ display: 'flex', justifyContent: 'center', py: 8 }}>
-            <CircularProgress />
+          <Box>
+            <Typography variant="h4" fontWeight="600" sx={{ mb: 3 }}>
+              Track Sleep
+            </Typography>
+            <Paper sx={{ p: 3, mb: 3 }}>
+              <FormSkeleton />
+            </Paper>
+            <Typography variant="h6" fontWeight="600" sx={{ mb: 2 }}>
+              Recent Sleep Activities
+            </Typography>
+            <ActivityListSkeleton count={3} />
           </Box>
         </AppShell>
       </ProtectedRoute>
@@ -536,9 +546,7 @@ export default function SleepTrackPage() {
               </Box>
 
               {sleepsLoading ? (
-                <Box sx={{ display: 'flex', justifyContent: 'center', py: 4 }}>
-                  <CircularProgress size={30} />
-                </Box>
+                <ActivityListSkeleton count={3} />
               ) : recentSleeps.length === 0 ? (
                 <Box sx={{ textAlign: 'center', py: 4 }}>
                   <Typography variant="body2" color="text.secondary">