feat(api-key): add independent quota and expiration support

This feature allows API Keys to have their own quota limits and expiration
times, independent of the user's balance.

Backend:
- Add quota, quota_used, expires_at fields to api_key schema
- Implement IsExpired() and IsQuotaExhausted() checks in middleware
- Add ResetQuota and ClearExpiration API endpoints
- Integrate quota billing in gateway handlers (OpenAI, Anthropic, Gemini)
- Include quota/expiration fields in auth cache for performance
- Expiration check returns 403, quota exhausted returns 429

Frontend:
- Add quota and expiration inputs to key create/edit dialog
- Add quick-select buttons for expiration (+7, +30, +90 days)
- Add reset quota confirmation dialog
- Add expires_at column to keys list
- Add i18n translations for new features (en/zh)

Migration:
- Add 045_add_api_key_quota.sql for new columns

frontend/src/types/index.ts

@@ -374,9 +374,12 @@ export interface ApiKey {
   key: string
   name: string
   group_id: number | null
-  status: 'active' | 'inactive'
+  status: 'active' | 'inactive' | 'quota_exhausted' | 'expired'
   ip_whitelist: string[]
   ip_blacklist: string[]
+  quota: number // Quota limit in USD (0 = unlimited)
+  quota_used: number // Used quota amount in USD
+  expires_at: string | null // Expiration time (null = never expires)
   created_at: string
   updated_at: string
   group?: Group
@@ -388,6 +391,8 @@ export interface CreateApiKeyRequest {
   custom_key?: string // Optional custom API Key
   ip_whitelist?: string[]
   ip_blacklist?: string[]
+  quota?: number // Quota limit in USD (0 = unlimited)
+  expires_in_days?: number // Days until expiry (null = never expires)
 }
 
 export interface UpdateApiKeyRequest {
@@ -396,6 +401,9 @@ export interface UpdateApiKeyRequest {
   status?: 'active' | 'inactive'
   ip_whitelist?: string[]
   ip_blacklist?: string[]
+  quota?: number // Quota limit in USD (null = no change, 0 = unlimited)
+  expires_at?: string | null // Expiration time (null = no change)
+  reset_quota?: boolean // Reset quota_used to 0
 }
 
 export interface CreateGroupRequest {