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/usagelog/usagelog.go

@@ -64,6 +64,8 @@ const (
 	FieldFirstTokenMs = "first_token_ms"
 	// FieldUserAgent holds the string denoting the user_agent field in the database.
 	FieldUserAgent = "user_agent"
+	// FieldIPAddress holds the string denoting the ip_address field in the database.
+	FieldIPAddress = "ip_address"
 	// FieldImageCount holds the string denoting the image_count field in the database.
 	FieldImageCount = "image_count"
 	// FieldImageSize holds the string denoting the image_size field in the database.
@@ -147,6 +149,7 @@ var Columns = []string{
 	FieldDurationMs,
 	FieldFirstTokenMs,
 	FieldUserAgent,
+	FieldIPAddress,
 	FieldImageCount,
 	FieldImageSize,
 	FieldCreatedAt,
@@ -199,6 +202,8 @@ var (
 	DefaultStream bool
 	// UserAgentValidator is a validator for the "user_agent" field. It is called by the builders before save.
 	UserAgentValidator func(string) error
+	// IPAddressValidator is a validator for the "ip_address" field. It is called by the builders before save.
+	IPAddressValidator func(string) error
 	// DefaultImageCount holds the default value on creation for the "image_count" field.
 	DefaultImageCount int
 	// ImageSizeValidator is a validator for the "image_size" field. It is called by the builders before save.
@@ -340,6 +345,11 @@ func ByUserAgent(opts ...sql.OrderTermOption) OrderOption {
 	return sql.OrderByField(FieldUserAgent, opts...).ToFunc()
 }
 
+// ByIPAddress orders the results by the ip_address field.
+func ByIPAddress(opts ...sql.OrderTermOption) OrderOption {
+	return sql.OrderByField(FieldIPAddress, opts...).ToFunc()
+}
+
 // ByImageCount orders the results by the image_count field.
 func ByImageCount(opts ...sql.OrderTermOption) OrderOption {
 	return sql.OrderByField(FieldImageCount, opts...).ToFunc()