feat: OpenAI OAuth账号显示Codex使用量

从响应头提取x-codex-*使用量信息并保存到账号Extra字段，
前端账号列表展示5h/7d窗口的使用进度条。

frontend/src/components/account/AccountUsageCell.vue

@@ -68,7 +68,31 @@
       <SetupTokenTimeWindow :account="account" />
     </template>
 
-    <!-- OpenAI accounts: no usage window API, show dash -->
+    <!-- OpenAI OAuth accounts: show Codex usage from extra field -->
+    <template v-else-if="account.platform === 'openai' && account.type === 'oauth'">
+      <div v-if="hasCodexUsage" class="space-y-1">
+        <!-- 5h Window (Secondary) -->
+        <UsageProgressBar
+          v-if="codexSecondaryUsedPercent !== null"
+          label="5h"
+          :utilization="codexSecondaryUsedPercent"
+          :resets-at="codexSecondaryResetAt"
+          color="indigo"
+        />
+
+        <!-- Weekly Window (Primary) -->
+        <UsageProgressBar
+          v-if="codexPrimaryUsedPercent !== null"
+          label="7d"
+          :utilization="codexPrimaryUsedPercent"
+          :resets-at="codexPrimaryResetAt"
+          color="emerald"
+        />
+      </div>
+      <div v-else class="text-xs text-gray-400">-</div>
+    </template>
+
+    <!-- Other accounts: no usage window -->
     <template v-else>
       <div class="text-xs text-gray-400">-</div>
     </template>
@@ -100,9 +124,44 @@ const showUsageWindows = computed(() =>
   props.account.type === 'oauth' || props.account.type === 'setup-token'
 )
 
+// OpenAI Codex usage computed properties
+const hasCodexUsage = computed(() => {
+  const extra = props.account.extra
+  return extra && (
+    extra.codex_primary_used_percent !== undefined ||
+    extra.codex_secondary_used_percent !== undefined
+  )
+})
+
+const codexPrimaryUsedPercent = computed(() => {
+  const extra = props.account.extra
+  if (!extra || extra.codex_primary_used_percent === undefined) return null
+  return extra.codex_primary_used_percent
+})
+
+const codexSecondaryUsedPercent = computed(() => {
+  const extra = props.account.extra
+  if (!extra || extra.codex_secondary_used_percent === undefined) return null
+  return extra.codex_secondary_used_percent
+})
+
+const codexPrimaryResetAt = computed(() => {
+  const extra = props.account.extra
+  if (!extra || extra.codex_primary_reset_after_seconds === undefined) return null
+  const resetTime = new Date(Date.now() + extra.codex_primary_reset_after_seconds * 1000)
+  return resetTime.toISOString()
+})
+
+const codexSecondaryResetAt = computed(() => {
+  const extra = props.account.extra
+  if (!extra || extra.codex_secondary_reset_after_seconds === undefined) return null
+  const resetTime = new Date(Date.now() + extra.codex_secondary_reset_after_seconds * 1000)
+  return resetTime.toISOString()
+})
+
 const loadUsage = async () => {
   // Only fetch usage for Anthropic OAuth accounts
-  // OpenAI doesn't have a usage window API - usage is updated from response headers during forwarding
+  // OpenAI usage comes from account.extra field (updated during forwarding)
   if (props.account.platform !== 'anthropic' || props.account.type !== 'oauth') return
 
   loading.value = true