feat: 实现注册优惠码功能

- 支持创建/编辑/删除优惠码，设置赠送金额和使用限制
  - 注册页面实时验证优惠码并显示赠送金额
  - 支持 URL 参数自动填充 (?promo=CODE)
  - 添加优惠码验证接口速率限制
  - 使用数据库行锁防止并发超限
  - 新增后台优惠码管理页面，支持复制注册链接

frontend/src/i18n/locales/en.ts

@@ -145,7 +145,8 @@ export default {
     copiedToClipboard: 'Copied to clipboard',
     copyFailed: 'Failed to copy',
     contactSupport: 'Contact Support',
-        selectOption: 'Select an option',
+    optional: 'optional',
+    selectOption: 'Select an option',
         searchPlaceholder: 'Search...', 
         noOptionsFound: 'No options found',
         noGroupsAvailable: 'No groups available',
@@ -177,6 +178,7 @@ export default {
     accounts: 'Accounts',
     proxies: 'Proxies',
     redeemCodes: 'Redeem Codes',
+    promoCodes: 'Promo Codes',
     settings: 'Settings',
     myAccount: 'My Account',
     lightMode: 'Light Mode',
@@ -229,6 +231,17 @@ export default {
     sendingCode: 'Sending...',
     clickToResend: 'Click to resend code',
     resendCode: 'Resend verification code',
+    promoCodeLabel: 'Promo Code',
+    promoCodePlaceholder: 'Enter promo code (optional)',
+    promoCodeValid: 'Valid! You will receive ${amount} bonus balance',
+    promoCodeInvalid: 'Invalid promo code',
+    promoCodeNotFound: 'Promo code not found',
+    promoCodeExpired: 'This promo code has expired',
+    promoCodeDisabled: 'This promo code is disabled',
+    promoCodeMaxUsed: 'This promo code has reached its usage limit',
+    promoCodeAlreadyUsed: 'You have already used this promo code',
+    promoCodeValidating: 'Promo code is being validated, please wait',
+    promoCodeInvalidCannotRegister: 'Invalid promo code. Please check and try again or clear the promo code field',
     linuxdo: {
       signIn: 'Continue with Linux.do',
       orContinue: 'or continue with email',
@@ -1722,6 +1735,65 @@ export default {
       }
     },
 
+    // Promo Codes
+    promo: {
+      title: 'Promo Code Management',
+      description: 'Create and manage registration promo codes',
+      createCode: 'Create Promo Code',
+      editCode: 'Edit Promo Code',
+      deleteCode: 'Delete Promo Code',
+      searchCodes: 'Search codes...',
+      allStatus: 'All Status',
+      columns: {
+        code: 'Code',
+        bonusAmount: 'Bonus Amount',
+        maxUses: 'Max Uses',
+        usedCount: 'Used',
+        usage: 'Usage',
+        status: 'Status',
+        expiresAt: 'Expires At',
+        createdAt: 'Created At',
+        actions: 'Actions'
+      },
+      // Form labels (flat structure for template usage)
+      code: 'Promo Code',
+      autoGenerate: 'auto-generate if empty',
+      codePlaceholder: 'Enter promo code or leave empty',
+      bonusAmount: 'Bonus Amount ($)',
+      maxUses: 'Max Uses',
+      zeroUnlimited: '0 = unlimited',
+      expiresAt: 'Expires At',
+      notes: 'Notes',
+      notesPlaceholder: 'Optional notes for this code',
+      status: 'Status',
+      neverExpires: 'Never expires',
+      // Status labels
+      statusActive: 'Active',
+      statusDisabled: 'Disabled',
+      statusExpired: 'Expired',
+      statusMaxUsed: 'Used Up',
+      // Usage records
+      usageRecords: 'Usage Records',
+      viewUsages: 'View Usages',
+      noUsages: 'No usage records yet',
+      userPrefix: 'User #{id}',
+      copied: 'Copied!',
+      // Messages
+      noCodesYet: 'No promo codes yet',
+      createFirstCode: 'Create your first promo code to offer registration bonuses.',
+      codeCreated: 'Promo code created successfully',
+      codeUpdated: 'Promo code updated successfully',
+      codeDeleted: 'Promo code deleted successfully',
+      deleteCodeConfirm: 'Are you sure you want to delete this promo code? This action cannot be undone.',
+      copyRegisterLink: 'Copy register link',
+      registerLinkCopied: 'Register link copied to clipboard',
+      failedToLoad: 'Failed to load promo codes',
+      failedToCreate: 'Failed to create promo code',
+      failedToUpdate: 'Failed to update promo code',
+      failedToDelete: 'Failed to delete promo code',
+      failedToLoadUsages: 'Failed to load usage records'
+    },
+
     // Usage Records
     usage: {
       title: 'Usage Records',

frontend/src/i18n/locales/zh.ts

@@ -142,6 +142,7 @@ export default {
     copiedToClipboard: '已复制到剪贴板',
     copyFailed: '复制失败',
     contactSupport: '联系客服',
+    optional: '可选',
     selectOption: '请选择',
     searchPlaceholder: '搜索...',
     noOptionsFound: '无匹配选项',
@@ -175,6 +176,7 @@ export default {
     accounts: '账号管理',
     proxies: 'IP管理',
     redeemCodes: '兑换码',
+    promoCodes: '优惠码',
     settings: '系统设置',
     myAccount: '我的账户',
     lightMode: '浅色模式',
@@ -227,6 +229,17 @@ export default {
     sendingCode: '发送中...',
     clickToResend: '点击重新发送验证码',
     resendCode: '重新发送验证码',
+    promoCodeLabel: '优惠码',
+    promoCodePlaceholder: '输入优惠码（可选）',
+    promoCodeValid: '有效！注册后将获得 ${amount} 赠送余额',
+    promoCodeInvalid: '无效的优惠码',
+    promoCodeNotFound: '优惠码不存在',
+    promoCodeExpired: '此优惠码已过期',
+    promoCodeDisabled: '此优惠码已被禁用',
+    promoCodeMaxUsed: '此优惠码已达到使用上限',
+    promoCodeAlreadyUsed: '您已使用过此优惠码',
+    promoCodeValidating: '优惠码正在验证中，请稍候',
+    promoCodeInvalidCannotRegister: '优惠码无效，请检查后重试或清空优惠码',
     linuxdo: {
       signIn: '使用 Linux.do 登录',
       orContinue: '或使用邮箱密码继续',
@@ -1867,6 +1880,65 @@ export default {
       failedToDelete: '删除兑换码失败'
     },
 
+    // Promo Codes
+    promo: {
+      title: '优惠码管理',
+      description: '创建和管理注册优惠码',
+      createCode: '创建优惠码',
+      editCode: '编辑优惠码',
+      deleteCode: '删除优惠码',
+      searchCodes: '搜索优惠码...',
+      allStatus: '全部状态',
+      columns: {
+        code: '优惠码',
+        bonusAmount: '赠送金额',
+        maxUses: '最大使用次数',
+        usedCount: '已使用',
+        usage: '使用量',
+        status: '状态',
+        expiresAt: '过期时间',
+        createdAt: '创建时间',
+        actions: '操作'
+      },
+      // 表单标签（扁平结构便于模板使用）
+      code: '优惠码',
+      autoGenerate: '留空自动生成',
+      codePlaceholder: '输入优惠码或留空',
+      bonusAmount: '赠送金额 ($)',
+      maxUses: '最大使用次数',
+      zeroUnlimited: '0 = 无限制',
+      expiresAt: '过期时间',
+      notes: '备注',
+      notesPlaceholder: '可选备注信息',
+      status: '状态',
+      neverExpires: '永不过期',
+      // 状态标签
+      statusActive: '启用',
+      statusDisabled: '禁用',
+      statusExpired: '已过期',
+      statusMaxUsed: '已用完',
+      // 使用记录
+      usageRecords: '使用记录',
+      viewUsages: '查看使用记录',
+      noUsages: '暂无使用记录',
+      userPrefix: '用户 #{id}',
+      copied: '已复制！',
+      // 消息
+      noCodesYet: '暂无优惠码',
+      createFirstCode: '创建您的第一个优惠码，为新用户提供注册奖励。',
+      codeCreated: '优惠码创建成功',
+      codeUpdated: '优惠码更新成功',
+      codeDeleted: '优惠码删除成功',
+      deleteCodeConfirm: '确定要删除此优惠码吗？此操作无法撤销。',
+      copyRegisterLink: '复制注册链接',
+      registerLinkCopied: '注册链接已复制到剪贴板',
+      failedToLoad: '加载优惠码失败',
+      failedToCreate: '创建优惠码失败',
+      failedToUpdate: '更新优惠码失败',
+      failedToDelete: '删除优惠码失败',
+      failedToLoadUsages: '加载使用记录失败'
+    },
+
     // Usage Records
     usage: {
       title: '使用记录',