feat(auth): 添加 Linux DO Connect OAuth 登录支持

- 新增 Linux DO OAuth 配置项和环境变量支持
- 实现 OAuth 授权流程和回调处理
- 前端添加 Linux DO 登录按钮和回调页面
- 支持通过 Linux DO 账号注册/登录
- 添加相关国际化文本

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/views/auth/LinuxDoCallbackView.vue

@@ -0,0 +1,119 @@
+<template>
+  <AuthLayout>
+    <div class="space-y-6">
+      <div class="text-center">
+        <h2 class="text-2xl font-bold text-gray-900 dark:text-white">
+          {{ t('auth.linuxdo.callbackTitle') }}
+        </h2>
+        <p class="mt-2 text-sm text-gray-500 dark:text-dark-400">
+          {{ isProcessing ? t('auth.linuxdo.callbackProcessing') : t('auth.linuxdo.callbackHint') }}
+        </p>
+      </div>
+
+      <transition name="fade">
+        <div
+          v-if="errorMessage"
+          class="rounded-xl border border-red-200 bg-red-50 p-4 dark:border-red-800/50 dark:bg-red-900/20"
+        >
+          <div class="flex items-start gap-3">
+            <div class="flex-shrink-0">
+              <Icon name="exclamationCircle" size="md" class="text-red-500" />
+            </div>
+            <div class="space-y-2">
+              <p class="text-sm text-red-700 dark:text-red-400">
+                {{ errorMessage }}
+              </p>
+              <router-link to="/login" class="btn btn-primary">
+                {{ t('auth.linuxdo.backToLogin') }}
+              </router-link>
+            </div>
+          </div>
+        </div>
+      </transition>
+    </div>
+  </AuthLayout>
+</template>
+
+<script setup lang="ts">
+import { onMounted, ref } from 'vue'
+import { useRoute, useRouter } from 'vue-router'
+import { useI18n } from 'vue-i18n'
+import { AuthLayout } from '@/components/layout'
+import Icon from '@/components/icons/Icon.vue'
+import { useAuthStore, useAppStore } from '@/stores'
+
+const route = useRoute()
+const router = useRouter()
+const { t } = useI18n()
+
+const authStore = useAuthStore()
+const appStore = useAppStore()
+
+const isProcessing = ref(true)
+const errorMessage = ref('')
+
+function parseFragmentParams(): URLSearchParams {
+  const raw = typeof window !== 'undefined' ? window.location.hash : ''
+  const hash = raw.startsWith('#') ? raw.slice(1) : raw
+  return new URLSearchParams(hash)
+}
+
+function sanitizeRedirectPath(path: string | null | undefined): string {
+  if (!path) return '/dashboard'
+  if (!path.startsWith('/')) return '/dashboard'
+  if (path.startsWith('//')) return '/dashboard'
+  if (path.includes('://')) return '/dashboard'
+  if (path.includes('\n') || path.includes('\r')) return '/dashboard'
+  return path
+}
+
+onMounted(async () => {
+  const params = parseFragmentParams()
+
+  const token = params.get('access_token') || ''
+  const redirect = sanitizeRedirectPath(
+    params.get('redirect') || (route.query.redirect as string | undefined) || '/dashboard'
+  )
+  const error = params.get('error')
+  const errorDesc = params.get('error_description') || params.get('error_message') || ''
+
+  if (error) {
+    errorMessage.value = errorDesc || error
+    appStore.showError(errorMessage.value)
+    isProcessing.value = false
+    return
+  }
+
+  if (!token) {
+    errorMessage.value = t('auth.linuxdo.callbackMissingToken')
+    appStore.showError(errorMessage.value)
+    isProcessing.value = false
+    return
+  }
+
+  try {
+    await authStore.setToken(token)
+    appStore.showSuccess(t('auth.loginSuccess'))
+    await router.replace(redirect)
+  } catch (e: unknown) {
+    const err = e as { message?: string; response?: { data?: { detail?: string } } }
+    errorMessage.value = err.response?.data?.detail || err.message || t('auth.loginFailed')
+    appStore.showError(errorMessage.value)
+    isProcessing.value = false
+  }
+})
+</script>
+
+<style scoped>
+.fade-enter-active,
+.fade-leave-active {
+  transition: all 0.3s ease;
+}
+
+.fade-enter-from,
+.fade-leave-to {
+  opacity: 0;
+  transform: translateY(-8px);
+}
+</style>
+