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/ModuleStoreView.vue

@@ -4,6 +4,7 @@ import { useApi } from '@/composables/useApi'
 import { useAuthStore } from '@/stores/auth'
 import type { Module } from '@/types'
 import { ShoppingCart, Package, Search, Filter, X, Check, Download, AlertCircle } from 'lucide-vue-next'
+import { safeFixed } from '@/utils/formatters'
 
 const api = useApi()
 const auth = useAuthStore()
@@ -252,7 +253,7 @@ onMounted(() => {
           <div>
             <div class="flex items-start justify-between gap-2 mb-1">
               <h3 class="text-base font-semibold text-neutral-100">{{ module.name }}</h3>
-              <span class="text-lg font-bold text-oxide-400 shrink-0">${{ module.price.toFixed(2) }}</span>
+              <span class="text-lg font-bold text-oxide-400 shrink-0">${{ safeFixed(module.price, 2) }}</span>
             </div>
             <p class="text-sm text-neutral-500 line-clamp-2">{{ module.description }}</p>
           </div>
@@ -385,7 +386,7 @@ onMounted(() => {
           <div class="bg-neutral-800/50 border border-neutral-700 rounded-lg p-4 flex items-center justify-between">
             <div>
               <p class="text-sm text-neutral-400 mb-1">One-time purchase</p>
-              <p class="text-2xl font-bold text-oxide-400">${{ selectedModule.price.toFixed(2) }}</p>
+              <p class="text-2xl font-bold text-oxide-400">${{ safeFixed(selectedModule.price, 2) }}</p>
             </div>
             <button
               v-if="!selectedModule.is_purchased"
@@ -436,7 +437,7 @@ onMounted(() => {
             </div>
             <div class="border-t border-neutral-700 pt-2 mt-2 flex items-center justify-between">
               <span class="text-base font-medium text-neutral-300">Total</span>
-              <span class="text-2xl font-bold text-oxide-400">${{ selectedModule.price.toFixed(2) }}</span>
+              <span class="text-2xl font-bold text-oxide-400">${{ safeFixed(selectedModule.price, 2) }}</span>
             </div>
           </div>