feat(gemini): 完善 Gemini OAuth 配额系统和用量显示

主要改动：
- 后端：重构 Gemini 配额服务，支持多层级配额策略（GCP Standard/Free, Google One, AI Studio, Code Assist）
- 后端：优化 OAuth 服务，增强 tier_id 识别和存储逻辑
- 后端：改进用量统计服务，支持不同平台的配额查询
- 后端：优化限流服务，增加临时解除调度状态管理
- 前端：统一四种授权方式的用量显示格式和徽标样式
- 前端：增强账户配额信息展示，支持多种配额类型
- 前端：改进创建和重新授权模态框的用户体验
- 国际化：完善中英文配额相关文案
- 移除 CHANGELOG.md 文件

测试：所有单元测试通过

frontend/src/components/account/AccountQuotaInfo.vue

@@ -65,32 +65,33 @@ const tierLabel = computed(() => {
   const creds = props.account.credentials as GeminiCredentials | undefined
 
   if (isCodeAssist.value) {
-    // GCP Code Assist: 显示 GCP tier
-    const tierMap: Record<string, string> = {
-      LEGACY: 'Free',
-      PRO: 'Pro',
-      ULTRA: 'Ultra',
-      'standard-tier': 'Standard',
-      'pro-tier': 'Pro',
-      'ultra-tier': 'Ultra'
-    }
-    return tierMap[creds?.tier_id || ''] || (creds?.tier_id ? 'GCP' : 'Unknown')
+    const tier = (creds?.tier_id || '').toString().trim().toLowerCase()
+    if (tier === 'gcp_enterprise') return 'GCP Enterprise'
+    if (tier === 'gcp_standard') return 'GCP Standard'
+    // Backward compatibility
+    const upper = (creds?.tier_id || '').toString().trim().toUpperCase()
+    if (upper.includes('ULTRA') || upper.includes('ENTERPRISE')) return 'GCP Enterprise'
+    if (upper) return `GCP ${upper}`
+    return 'GCP'
   }
 
   if (isGoogleOne.value) {
-    // Google One: tier 映射
-    const tierMap: Record<string, string> = {
-      AI_PREMIUM: 'AI Premium',
-      GOOGLE_ONE_STANDARD: 'Standard',
-      GOOGLE_ONE_BASIC: 'Basic',
-      FREE: 'Free',
-      GOOGLE_ONE_UNKNOWN: 'Personal',
-      GOOGLE_ONE_UNLIMITED: 'Unlimited'
-    }
-    return tierMap[creds?.tier_id || ''] || 'Personal'
+    const tier = (creds?.tier_id || '').toString().trim().toLowerCase()
+    if (tier === 'google_ai_ultra') return 'Google AI Ultra'
+    if (tier === 'google_ai_pro') return 'Google AI Pro'
+    if (tier === 'google_one_free') return 'Google One Free'
+    // Backward compatibility
+    const upper = (creds?.tier_id || '').toString().trim().toUpperCase()
+    if (upper === 'AI_PREMIUM') return 'Google AI Pro'
+    if (upper === 'GOOGLE_ONE_UNLIMITED') return 'Google AI Ultra'
+    if (upper) return `Google One ${upper}`
+    return 'Google One'
   }
 
   // API Key: 显示 AI Studio
+  const tier = (creds?.tier_id || '').toString().trim().toLowerCase()
+  if (tier === 'aistudio_paid') return 'AI Studio Pay-as-you-go'
+  if (tier === 'aistudio_free') return 'AI Studio Free Tier'
   return 'AI Studio'
 })
 
@@ -99,35 +100,31 @@ const tierBadgeClass = computed(() => {
   const creds = props.account.credentials as GeminiCredentials | undefined
 
   if (isCodeAssist.value) {
-    // GCP Code Assist 样式
-    const tierColorMap: Record<string, string> = {
-      LEGACY: 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300',
-      PRO: 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300',
-      ULTRA: 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300',
-      'standard-tier': 'bg-green-100 text-green-600 dark:bg-green-900/40 dark:text-green-300',
-      'pro-tier': 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300',
-      'ultra-tier': 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300'
-    }
-    return (
-      tierColorMap[creds?.tier_id || ''] ||
-      'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300'
-    )
+    const tier = (creds?.tier_id || '').toString().trim().toLowerCase()
+    if (tier === 'gcp_enterprise') return 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300'
+    if (tier === 'gcp_standard') return 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300'
+    // Backward compatibility
+    const upper = (creds?.tier_id || '').toString().trim().toUpperCase()
+    if (upper.includes('ULTRA') || upper.includes('ENTERPRISE')) return 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300'
+    return 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300'
   }
 
   if (isGoogleOne.value) {
-    // Google One tier 样式
-    const tierColorMap: Record<string, string> = {
-      AI_PREMIUM: 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300',
-      GOOGLE_ONE_STANDARD: 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300',
-      GOOGLE_ONE_BASIC: 'bg-green-100 text-green-600 dark:bg-green-900/40 dark:text-green-300',
-      FREE: 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300',
-      GOOGLE_ONE_UNKNOWN: 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300',
-      GOOGLE_ONE_UNLIMITED: 'bg-amber-100 text-amber-600 dark:bg-amber-900/40 dark:text-amber-300'
-    }
-    return tierColorMap[creds?.tier_id || ''] || 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300'
+    const tier = (creds?.tier_id || '').toString().trim().toLowerCase()
+    if (tier === 'google_ai_ultra') return 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300'
+    if (tier === 'google_ai_pro') return 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300'
+    if (tier === 'google_one_free') return 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300'
+    // Backward compatibility
+    const upper = (creds?.tier_id || '').toString().trim().toUpperCase()
+    if (upper === 'GOOGLE_ONE_UNLIMITED') return 'bg-purple-100 text-purple-600 dark:bg-purple-900/40 dark:text-purple-300'
+    if (upper === 'AI_PREMIUM') return 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300'
+    return 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300'
   }
 
   // AI Studio 默认样式：蓝色
+  const tier = (creds?.tier_id || '').toString().trim().toLowerCase()
+  if (tier === 'aistudio_paid') return 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300'
+  if (tier === 'aistudio_free') return 'bg-gray-100 text-gray-600 dark:bg-gray-700 dark:text-gray-300'
   return 'bg-blue-100 text-blue-600 dark:bg-blue-900/40 dark:text-blue-300'
 })