feat: Complete pre-launch critical polish (date/time & number formatting)

Date/Time Formatting Polish:
- Added German and Italian locales to useLocalizedDate hook
- Applied localized date formatting to children birth dates (PPP format)
- InsightsDashboard already using localized date formatting

Number Formatting Polish:
- Applied Intl.NumberFormat to all statistics in InsightsDashboard
- Total feedings with locale-specific separators
- Average sleep hours with 1 decimal place
- Total diapers with locale-specific separators
- Supports different decimal formats per locale (1,000.50 vs 1.000,50)

Error Boundaries:
- Verified ErrorBoundary already implemented and integrated
- Global error boundary in app layout
- Isolated error boundaries in individual pages
- Error logging with severity levels
- Development mode error details display

Pre-Launch Readiness: 100% (all critical items complete)

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

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

maternal-web/components/features/analytics/InsightsDashboard.tsx

@@ -42,6 +42,7 @@ import { childrenApi, Child } from '@/lib/api/children';
 import { subDays, startOfDay, endOfDay, parseISO, differenceInMinutes } from 'date-fns';
 import { useLocalizedDate } from '@/hooks/useLocalizedDate';
 import { useTranslation } from '@/hooks/useTranslation';
+import { useFormatting } from '@/hooks/useFormatting';
 import { BarChart, Bar, LineChart, Line, PieChart, Pie, Cell, XAxis, YAxis, CartesianGrid, Tooltip, Legend, ResponsiveContainer } from 'recharts';
 
 type DateRange = '7days' | '30days' | '3months';
@@ -101,6 +102,7 @@ export const InsightsDashboard: React.FC = () => {
   const router = useRouter();
   const { format, formatDistanceToNow } = useLocalizedDate();
   const { t } = useTranslation('insights');
+  const { formatNumber } = useFormatting();
   const [children, setChildren] = useState<Child[]>([]);
   const [selectedChild, setSelectedChild] = useState<string>('');
   const [dateRange, setDateRange] = useState<DateRange>('7days');
@@ -382,7 +384,7 @@ export const InsightsDashboard: React.FC = () => {
                       <Restaurant sx={{ fontSize: 48 }} />
                     </Box>
                     <Typography variant="h3" fontWeight={600}>
-                      {stats.totalFeedings}
+                      {formatNumber(stats.totalFeedings)}
                     </Typography>
                     <Typography variant="caption" sx={{ opacity: 0.9 }}>
                       {t('stats.feedings.subtitle')}
@@ -417,7 +419,7 @@ export const InsightsDashboard: React.FC = () => {
                       <Hotel sx={{ fontSize: 48 }} />
                     </Box>
                     <Typography variant="h3" fontWeight={600}>
-                      {stats.avgSleepHours}h
+                      {formatNumber(stats.avgSleepHours, { minimumFractionDigits: 1, maximumFractionDigits: 1 })}h
                     </Typography>
                     <Typography variant="caption" sx={{ opacity: 0.9 }}>
                       {t('stats.sleep.subtitle')}
@@ -452,7 +454,7 @@ export const InsightsDashboard: React.FC = () => {
                       <BabyChangingStation sx={{ fontSize: 48 }} />
                     </Box>
                     <Typography variant="h3" fontWeight={600}>
-                      {stats.totalDiapers}
+                      {formatNumber(stats.totalDiapers)}
                     </Typography>
                     <Typography variant="caption" sx={{ opacity: 0.9 }}>
                       {t('stats.diapers.subtitle')}