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

backend/internal/service/api_key_auth_cache.go

@@ -1,5 +1,7 @@
 package service
 
+import "time"
+
 // APIKeyAuthSnapshot API Key 认证缓存快照（仅包含认证所需字段）
 type APIKeyAuthSnapshot struct {
 	APIKeyID    int64                    `json:"api_key_id"`
@@ -10,6 +12,13 @@ type APIKeyAuthSnapshot struct {
 	IPBlacklist []string                 `json:"ip_blacklist,omitempty"`
 	User        APIKeyAuthUserSnapshot   `json:"user"`
 	Group       *APIKeyAuthGroupSnapshot `json:"group,omitempty"`
+
+	// Quota fields for API Key independent quota feature
+	Quota     float64 `json:"quota"`      // Quota limit in USD (0 = unlimited)
+	QuotaUsed float64 `json:"quota_used"` // Used quota amount
+
+	// Expiration field for API Key expiration feature
+	ExpiresAt *time.Time `json:"expires_at,omitempty"` // Expiration time (nil = never expires)
 }
 
 // APIKeyAuthUserSnapshot 用户快照