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_impl.go

@@ -213,6 +213,9 @@ func (s *APIKeyService) snapshotFromAPIKey(apiKey *APIKey) *APIKeyAuthSnapshot {
 		Status:      apiKey.Status,
 		IPWhitelist: apiKey.IPWhitelist,
 		IPBlacklist: apiKey.IPBlacklist,
+		Quota:       apiKey.Quota,
+		QuotaUsed:   apiKey.QuotaUsed,
+		ExpiresAt:   apiKey.ExpiresAt,
 		User: APIKeyAuthUserSnapshot{
 			ID:          apiKey.User.ID,
 			Status:      apiKey.User.Status,
@@ -256,6 +259,9 @@ func (s *APIKeyService) snapshotToAPIKey(key string, snapshot *APIKeyAuthSnapsho
 		Status:      snapshot.Status,
 		IPWhitelist: snapshot.IPWhitelist,
 		IPBlacklist: snapshot.IPBlacklist,
+		Quota:       snapshot.Quota,
+		QuotaUsed:   snapshot.QuotaUsed,
+		ExpiresAt:   snapshot.ExpiresAt,
 		User: &User{
 			ID:          snapshot.User.ID,
 			Status:      snapshot.User.Status,