feat: 通用授权后台、离线证、Waffo 支付页与仪表盘加强

支持多产品计划展示、LICOFF 离线签发、支付独立配置与调试，以及分析看板；同步更新 README 与集成文档。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/utils/offline_license_test.go

@@ -0,0 +1,75 @@
+package utils
+
+import (
+	"testing"
+	"time"
+)
+
+func TestOfflineLicenseSignAndVerify(t *testing.T) {
+	kp, err := DeriveOfflineKeyPair("319de107090c6fd0aae9b7db343376dd5a22ccfb24b631ee67144141b1d32000")
+	if err != nil {
+		t.Fatal(err)
+	}
+	now := time.Now().Unix()
+	claims := OfflineLicenseClaims{
+		ProductCode: "opsxshell",
+		DeviceID:    "dev-1",
+		Email:       "a@b.com",
+		PlanType:    "yearly",
+		IssuedAt:    now,
+		ExpiresAt:   now + 86400*30,
+		MaxDevices:  1,
+	}
+	serial, err := SignOfflineLicense(kp, claims)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !IsOfflineLicenseKey(serial) {
+		t.Fatalf("prefix: %s", serial)
+	}
+	got, err := VerifyOfflineLicense(kp.Public, serial)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.DeviceID != "dev-1" || got.PlanType != "yearly" {
+		t.Fatalf("claims mismatch: %+v", got)
+	}
+}
+
+func TestOfflineLicenseRejectsPerpetual(t *testing.T) {
+	kp, err := DeriveOfflineKeyPair("319de107090c6fd0aae9b7db343376dd5a22ccfb24b631ee67144141b1d32000")
+	if err != nil {
+		t.Fatal(err)
+	}
+	now := time.Now().Unix()
+	_, err = SignOfflineLicense(kp, OfflineLicenseClaims{
+		ProductCode: "opsxshell",
+		DeviceID:    "dev-1",
+		PlanType:    "perpetual",
+		IssuedAt:    now,
+		ExpiresAt:   now + 86400,
+		MaxDevices:  1,
+	})
+	if err == nil {
+		t.Fatal("expected perpetual reject")
+	}
+}
+
+func TestOfflineLicenseRejectsOver365(t *testing.T) {
+	kp, err := DeriveOfflineKeyPair("319de107090c6fd0aae9b7db343376dd5a22ccfb24b631ee67144141b1d32000")
+	if err != nil {
+		t.Fatal(err)
+	}
+	now := time.Now().Unix()
+	_, err = SignOfflineLicense(kp, OfflineLicenseClaims{
+		ProductCode: "opsxshell",
+		DeviceID:    "dev-1",
+		PlanType:    "yearly",
+		IssuedAt:    now,
+		ExpiresAt:   now + 86400*400,
+		MaxDevices:  1,
+	})
+	if err == nil {
+		t.Fatal("expected over-365 reject")
+	}
+}