feat(api-key): 添加 IP 白名单/黑名单限制功能 (#221)

* feat(api-key): add IP whitelist/blacklist restriction and usage log IP tracking

- Add IP restriction feature for API keys (whitelist/blacklist with CIDR support)
- Add IP address logging to usage logs (admin-only visibility)
- Remove billing_type column from usage logs UI (redundant)
- Use generic "Access denied" error message for security

Backend:
- New ip package with IP/CIDR validation and matching utilities
- Database migrations for ip_whitelist, ip_blacklist (api_keys) and ip_address (usage_logs)
- Middleware IP restriction check after API key validation
- Input validation for IP/CIDR patterns on create/update

Frontend:
- API key form with enable toggle for IP restriction
- Shield icon indicator in table for keys with IP restriction
- Removed billing_type filter and column from usage views

* fix: update API contract tests for ip_whitelist/ip_blacklist fields

Add ip_whitelist and ip_blacklist fields to expected JSON responses
in API contract tests to match the new API key schema.

backend/ent/apikey/where.go

@@ -470,6 +470,26 @@ func StatusContainsFold(v string) predicate.APIKey {
 	return predicate.APIKey(sql.FieldContainsFold(FieldStatus, v))
 }
 
+// IPWhitelistIsNil applies the IsNil predicate on the "ip_whitelist" field.
+func IPWhitelistIsNil() predicate.APIKey {
+	return predicate.APIKey(sql.FieldIsNull(FieldIPWhitelist))
+}
+
+// IPWhitelistNotNil applies the NotNil predicate on the "ip_whitelist" field.
+func IPWhitelistNotNil() predicate.APIKey {
+	return predicate.APIKey(sql.FieldNotNull(FieldIPWhitelist))
+}
+
+// IPBlacklistIsNil applies the IsNil predicate on the "ip_blacklist" field.
+func IPBlacklistIsNil() predicate.APIKey {
+	return predicate.APIKey(sql.FieldIsNull(FieldIPBlacklist))
+}
+
+// IPBlacklistNotNil applies the NotNil predicate on the "ip_blacklist" field.
+func IPBlacklistNotNil() predicate.APIKey {
+	return predicate.APIKey(sql.FieldNotNull(FieldIPBlacklist))
+}
+
 // HasUser applies the HasEdge predicate on the "user" edge.
 func HasUser() predicate.APIKey {
 	return predicate.APIKey(func(s *sql.Selector) {