feat: Refactor CLI API client by splitting billing, carrier, and charging modules into separate files

- Extract Invoice, Payment, Subscriber types and GetInvoices, GetPayments, GenerateInvoice methods to billing.go
- Extract CarrierInfo, ConnectivityStatus, ProfileInfo types and carrier connector methods to carrier.go
- Extract CreditCheckRequest/Response, CreditBalanceResponse types and charging engine methods to charging.go
- Add PacketStats, CreditInfo types and GetPacketStats, GetCreditInfo

apps/cli/internal/api/carrier.go

@@ -0,0 +1,70 @@
+package api
+
+// Carrier Connector Integration
+type CarrierInfo struct {
+	Name        string `json:"name"`
+	Country     string `json:"country"`
+	NetworkType string `json:"network_type"`
+	Status      string `json:"status"`
+}
+
+type ConnectivityStatus struct {
+	Connected bool   `json:"connected"`
+	Latency   string `json:"latency"`
+	Message   string `json:"message"`
+}
+
+type ProfileInfo struct {
+	ProfileID      string `json:"profile_id"`
+	IMSI           string `json:"imsi"`
+	Status         string `json:"status"`
+	ActivationCode string `json:"activation_code"`
+}
+
+type OrderProfileRequest struct {
+	IMSI      string `json:"imsi"`
+	ProfileID string `json:"profile_id"`
+}
+
+// GetCarrierInfo retrieves carrier information
+func (c *Client) GetCarrierInfo() (*CarrierInfo, error) {
+	var info CarrierInfo
+	if err := c.doGetJSON("/api/v1/carrier/info", &info); err != nil {
+		return nil, err
+	}
+	return &info, nil
+}
+
+// CheckConnectivity checks carrier connectivity
+func (c *Client) CheckConnectivity() (*ConnectivityStatus, error) {
+	var status ConnectivityStatus
+	if err := c.doGetJSON("/api/v1/carrier/connectivity", &status); err != nil {
+		return nil, err
+	}
+	return &status, nil
+}
+
+// ListProfiles lists eSIM profiles
+func (c *Client) ListProfiles() ([]ProfileInfo, error) {
+	var resp struct {
+		Data []ProfileInfo `json:"data"`
+	}
+	if err := c.doGetJSON("/api/v1/esim/profiles", &resp); err != nil {
+		return nil, err
+	}
+	return resp.Data, nil
+}
+
+// OrderProfile orders a new eSIM profile
+func (c *Client) OrderProfile(req *OrderProfileRequest) (*ProfileInfo, error) {
+	var profile ProfileInfo
+	if err := c.doPostJSON("/api/v1/esim/profiles", req, &profile); err != nil {
+		return nil, err
+	}
+	return &profile, nil
+}
+
+// DeleteProfile deletes an eSIM profile
+func (c *Client) DeleteProfile(profileID string) error {
+	return c.doDelete("/api/v1/esim/profiles/" + profileID)
+}