feat: 添加版本更新检查功能

- 后端新增 /api/admin/system/check-update 接口，从 GitHub Tags 获取最新版本
- 前端新增 UpdateDialog 组件，管理员登录后自动检查更新并弹窗提示
- 同一会话内只检查一次，点击"稍后提醒"后 24 小时内不再提示
- CI 和 deploy.sh 自动生成 _version.py 版本文件

frontend/src/components/common/UpdateDialog.vue

@@ -0,0 +1,112 @@
+<template>
+  <Dialog
+    v-model="isOpen"
+    size="md"
+    title=""
+  >
+    <div class="flex flex-col items-center text-center py-2">
+      <!-- Logo -->
+      <HeaderLogo
+        size="h-16 w-16"
+        class-name="text-primary"
+      />
+
+      <!-- Title -->
+      <h2 class="text-xl font-semibold text-foreground mt-4 mb-2">
+        发现新版本
+      </h2>
+
+      <!-- Version Info -->
+      <div class="flex items-center gap-3 mb-4">
+        <span class="px-3 py-1.5 rounded-lg bg-muted text-sm font-mono text-muted-foreground">
+          v{{ currentVersion }}
+        </span>
+        <svg
+          class="h-4 w-4 text-muted-foreground"
+          fill="none"
+          stroke="currentColor"
+          viewBox="0 0 24 24"
+        >
+          <path
+            stroke-linecap="round"
+            stroke-linejoin="round"
+            stroke-width="2"
+            d="M13 7l5 5m0 0l-5 5m5-5H6"
+          />
+        </svg>
+        <span class="px-3 py-1.5 rounded-lg bg-primary/10 text-sm font-mono font-medium text-primary">
+          v{{ latestVersion }}
+        </span>
+      </div>
+
+      <!-- Description -->
+      <p class="text-sm text-muted-foreground max-w-xs">
+        新版本已发布，建议更新以获得最新功能和安全修复
+      </p>
+    </div>
+
+    <template #footer>
+      <div class="flex w-full gap-3">
+        <Button
+          variant="outline"
+          class="flex-1"
+          @click="handleLater"
+        >
+          稍后提醒
+        </Button>
+        <Button
+          class="flex-1"
+          @click="handleViewRelease"
+        >
+          查看更新
+        </Button>
+      </div>
+    </template>
+  </Dialog>
+</template>
+
+<script setup lang="ts">
+import { ref, watch } from 'vue'
+import { Dialog } from '@/components/ui'
+import Button from '@/components/ui/button.vue'
+import HeaderLogo from '@/components/HeaderLogo.vue'
+
+const props = defineProps<{
+  modelValue: boolean
+  currentVersion: string
+  latestVersion: string
+  releaseUrl: string | null
+}>()
+
+const emit = defineEmits<{
+  'update:modelValue': [value: boolean]
+}>()
+
+const isOpen = ref(props.modelValue)
+
+watch(() => props.modelValue, (val) => {
+  isOpen.value = val
+})
+
+watch(isOpen, (val) => {
+  emit('update:modelValue', val)
+})
+
+function handleLater() {
+  // 记录忽略的版本，24小时内不再提醒
+  const ignoreKey = 'aether_update_ignore'
+  const ignoreData = {
+    version: props.latestVersion,
+    until: Date.now() + 24 * 60 * 60 * 1000 // 24小时
+  }
+  localStorage.setItem(ignoreKey, JSON.stringify(ignoreData))
+  isOpen.value = false
+}
+
+function handleViewRelease() {
+  if (props.releaseUrl) {
+    window.open(props.releaseUrl, '_blank')
+  }
+  isOpen.value = false
+}
+</script>