fix(admin-service): relax changelog and minOsVersion validation

- Changelog: allow empty value, return default "No changelog provided"
- MinOsVersion: allow empty value and single number format (e.g., "24" -> "24.0")

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/admin-service/src/domain/value-objects/changelog.vo.ts

@@ -15,16 +15,13 @@ export class Changelog {
   }
 
   static create(value: string): Changelog {
+    // 允许空值，返回默认 changelog
     if (!value || value.trim() === '') {
-      throw new DomainException('Changelog cannot be empty');
+      return Changelog.empty();
     }
 
     const trimmed = value.trim();
 
-    if (trimmed.length < 10) {
-      throw new DomainException('Changelog must be at least 10 characters');
-    }
-
     if (trimmed.length > 5000) {
       throw new DomainException('Changelog cannot exceed 5000 characters');
     }

backend/services/admin-service/src/domain/value-objects/min-os-version.vo.ts

@@ -15,12 +15,18 @@ export class MinOsVersion {
   }
 
   static create(value: string): MinOsVersion {
+    // 允许空值，返回默认版本
     if (!value || value.trim() === '') {
-      throw new DomainException('MinOsVersion cannot be empty');
+      return MinOsVersion.none();
     }
 
     const trimmed = value.trim();
 
+    // 支持纯数字格式 (e.g., "24") 自动转换为 "24.0"
+    if (/^\d+$/.test(trimmed)) {
+      return new MinOsVersion(`${trimmed}.0`);
+    }
+
     // 验证格式: 数字.数字 或 数字.数字.数字 (e.g., "11.0", "14.0", "5.1.1")
     if (!/^\d+(\.\d+){1,2}$/.test(trimmed)) {
       throw new DomainException('MinOsVersion must be in format like "11.0" or "5.1.1"');