导航: 统一分区侧栏 + 新增用量统计页

- ShellLayout 按所在分区显示独立菜单:
  用户控制台(/console) 与 管理后台(/admin) 不混排, 各带跨区跳转(管理→/返回控制台→)
- /console 与 /admin 共用 ShellLayout, 移除 ConsoleLayout/AdminLayout 薄包装
- 新增 /admin/usage 用量统计页(全局请求明细, 按模型过滤+分页)

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

web/src/views/console/ConsoleLayout.vue

@@ -1,38 +0,0 @@
-<script setup lang="ts">
-import { computed } from 'vue'
-import { useAuthStore } from '@/stores/auth'
-import ShellLayout from '@/components/layout/ShellLayout.vue'
-
-const auth = useAuthStore()
-const sections = computed(() => {
-  const s: { title: string; items: { to: string; label: string }[] }[] = [
-    {
-      title: '控制台',
-      items: [
-        { to: '/console/dashboard', label: '仪表盘' },
-        { to: '/console/keys', label: 'API Keys' },
-        { to: '/console/usage', label: '用量' },
-      ],
-    },
-  ]
-  if (auth.isAdmin) {
-    s.push({
-      title: '管理',
-      items: [
-        { to: '/admin/overview', label: '运营总览' },
-        { to: '/admin/channels', label: '渠道' },
-        { to: '/admin/models', label: '模型与定价' },
-        { to: '/admin/users', label: '用户' },
-        { to: '/admin/config', label: '系统配置' },
-      ],
-    })
-  }
-  return s
-})
-</script>
-
-<template>
-  <ShellLayout :sections="sections">
-    <router-view />
-  </ShellLayout>
-</template>