feat: Library 批量注册 + PeopleView 修复 + 国际化

Library:
- 添加 checkbox 和鼠标框选功能
- Unregistered 卡片添加快速注册按钮
- 状态标签移至左下方，人脸图标移至左侧中间
- Deep Scan 改为 unregister -> register -> process
- 完整国际化（日语、繁体中文、英语）

PeopleView:
- 修复卡片不显示问题（使用 get_file_traces API）
- 移除对 identity_id 字段的依赖

其他:
- 添加日语语言包
- 添加 useDragSelect composable
- 新增文档：Face Bbox Null Bug Report

src/stores/themeStore.ts

@@ -0,0 +1,32 @@
+import { ref, watch, onMounted } from 'vue'
+
+const THEME_KEY = 'momentry_theme'
+const saved = localStorage.getItem(THEME_KEY) || 'auto'
+const theme = ref(saved)
+
+function applyTheme(t: string) {
+  if (t === 'auto') {
+    const prefersDark = window.matchMedia('(prefers-color-scheme: dark)').matches
+    document.documentElement.setAttribute('data-theme', prefersDark ? 'dark' : 'light')
+  } else {
+    document.documentElement.setAttribute('data-theme', t)
+  }
+}
+
+watch(theme, (v) => {
+  localStorage.setItem(THEME_KEY, v)
+  applyTheme(v)
+})
+
+export function useTheme() {
+  onMounted(() => applyTheme(theme.value))
+
+  function toggleTheme() {
+    const current = theme.value === 'auto' 
+      ? (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light')
+      : theme.value
+    theme.value = current === 'dark' ? 'light' : 'dark'
+  }
+
+  return { theme, toggleTheme }
+}