fix: Replace unsafe .toFixed() calls with safeFixed() in analytics views

- AnalyticsView: avg_players, uptime_percentage
- WipeAnalyticsView: success_rate, population curve, durations, CSV export
- PlayerRetentionView: retention percentages, session duration, tooltip
- MapAnalyticsView: rotation effectiveness, performance metrics, table

All analytics views now use safe formatter utilities with optional chaining
to prevent null/undefined runtime errors when displaying numeric data.

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

frontend/src/views/admin/MigrationView.vue

@@ -2,6 +2,7 @@
 import { ref, onMounted } from 'vue'
 import { useApi } from '@/composables/useApi'
 import { Download, Upload, FileText, Loader2 } from 'lucide-vue-next'
+import { safeFileSize, safeDate } from '@/utils/formatters'
 
 interface ExportRecord {
   id: string
@@ -69,11 +70,7 @@ async function importData() {
 }
 
 function formatBytes(bytes: number): string {
-  if (bytes === 0) return '0 B'
-  const k = 1024
-  const sizes = ['B', 'KB', 'MB', 'GB']
-  const i = Math.floor(Math.log(bytes) / Math.log(k))
-  return `${(bytes / Math.pow(k, i)).toFixed(2)} ${sizes[i]}`
+  return safeFileSize(bytes)
 }
 
 onMounted(() => {
@@ -139,7 +136,7 @@ onMounted(() => {
         <tbody class="divide-y divide-neutral-800">
           <tr v-for="exp in exports" :key="exp.id" class="hover:bg-neutral-800/30">
             <td class="px-4 py-3 text-sm text-neutral-200 capitalize">{{ exp.export_type.replace('_', ' ') }}</td>
-            <td class="px-4 py-3 text-sm text-neutral-400">{{ new Date(exp.created_at).toLocaleString() }}</td>
+            <td class="px-4 py-3 text-sm text-neutral-400">{{ safeDate(exp.created_at) }}</td>
             <td class="px-4 py-3 text-sm text-neutral-400">{{ formatBytes(exp.file_size_bytes) }}</td>
             <td class="px-4 py-3">
               <a