feat: auto-generate license file on download if missing

Add AppService.ensureLicenseFile() that generates and persists a license
file when the app doesn't have one yet. Update AppController.downloadLicenseFile
to use it instead of throwing "License file not generated yet".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tenant-service/src/main/java/com/xuqm/tenant/controller/AppController.java

@@ -164,10 +164,7 @@ public class AppController {
     public ResponseEntity<byte[]> downloadLicenseFile(@PathVariable String appKey,
                                                        @AuthenticationPrincipal String tenantId) {
         AppEntity app = appService.getByAppKey(appKey, tenantId);
-        String encrypted = app.getLicenseFileContent();
-        if (encrypted == null || encrypted.isBlank()) {
-            throw new BusinessException("License file not generated yet");
-        }
+        String encrypted = appService.ensureLicenseFile(appKey, tenantId);
         String filename = sanitizeFileName(app.getName()) + ".xuqmlicense";
         return ResponseEntity.ok()
                 .contentType(MediaType.APPLICATION_OCTET_STREAM)

tenant-service/src/main/java/com/xuqm/tenant/service/AppService.java

@@ -12,6 +12,7 @@ import com.xuqm.tenant.config.PrivateDeploymentProperties;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
 
 import java.security.SecureRandom;
 import java.time.LocalDateTime;
@@ -89,6 +90,18 @@ public class AppService {
         return saved;
     }
 
+    @Transactional
+    public String ensureLicenseFile(String appKey, String tenantId) {
+        AppEntity app = getByAppKey(appKey, tenantId);
+        String content = app.getLicenseFileContent();
+        if (content == null || content.isBlank()) {
+            content = generateLicenseFileContent(app);
+            app.setLicenseFileContent(content);
+            appRepository.save(app);
+        }
+        return content;
+    }
+
     public AppEntity update(String appKey, String tenantId, CreateAppRequest req) {
         AppEntity app = getByAppKey(appKey, tenantId);
         Map<String, Object> before = new LinkedHashMap<>();