fix(frontend): change time format to 12-hour with AM/PM

- Change time locale from zh-CN to en-US to properly display AM/PM
- Increase letter-spacing for better readability (0.08em → 0.12em)
- Update all time displays to use 12-hour format consistently

frontend/src/pages/chat/chatPage.css

@@ -2155,7 +2155,7 @@
 .jarvis-time {
   font-family: var(--font-mono);
   font-size: 12px;
-  letter-spacing: 0.08em;
+  letter-spacing: 0.12em;
   color: rgba(224, 248, 255, 0.86);
 }
 

frontend/src/pages/chat/composables/useClientTime.ts

@@ -36,7 +36,7 @@ export function useClientTime() {
   }
 
   function formatClientClock(date: Date) {
-    return date.toLocaleTimeString('zh-CN', { hour12: false, hour: '2-digit', minute: '2-digit', second: '2-digit' })
+    return date.toLocaleTimeString('en-US', { hour12: true, hour: '2-digit', minute: '2-digit', second: '2-digit' })
   }
 
   function weatherCodeLabel(code: number | null | undefined) {

frontend/src/pages/chat/index.vue

@@ -230,7 +230,7 @@ function renderMarkdown(content: string) {
           <div class="jarvis-date-row">
             <div class="jarvis-date-meta">
               <div class="jarvis-month">{{ clientTime.toLocaleString('zh-CN', { month: 'long' }) }} {{ clientTime.getFullYear() }}</div>
-              <div class="jarvis-time">{{ clientTime.toLocaleTimeString('zh-CN', { hour12: false }) }}</div>
+              <div class="jarvis-time">{{ clientTime.toLocaleTimeString('en-US', { hour12: true }) }}</div>
             </div>
             <div class="jarvis-location">
               <div class="location-info">