replace all hardcoded en-US and $ formatting with locale-aware helpers

src/views/Timer.vue

@@ -87,7 +87,7 @@
           </div>
           <div class="text-right">
             <p class="text-[0.75rem] font-mono text-text-primary">{{ formatDuration(entry.duration) }}</p>
-            <p class="text-[0.6875rem] text-text-tertiary">{{ formatDate(entry.start_time) }}</p>
+            <p class="text-[0.6875rem] text-text-tertiary">{{ formatDateTime(entry.start_time) }}</p>
           </div>
         </div>
       </div>
@@ -110,6 +110,7 @@ import { useEntriesStore } from '../stores/entries'
 import { useToastStore } from '../stores/toast'
 import { Timer as TimerIcon } from 'lucide-vue-next'
 import AppSelect from '../components/AppSelect.vue'
+import { formatDateTime } from '../utils/locale'
 
 const timerStore = useTimerStore()
 const projectsStore = useProjectsStore()
@@ -200,17 +201,6 @@ function formatDuration(seconds: number): string {
   return `${minutes}m`
 }
 
-// Format date
-function formatDate(dateString: string): string {
-  const date = new Date(dateString)
-  return date.toLocaleDateString('en-US', {
-    month: 'short',
-    day: 'numeric',
-    hour: '2-digit',
-    minute: '2-digit'
-  })
-}
-
 // Load data on mount
 onMounted(async () => {
   await Promise.all([