refactor: organize tests and extract formatting utilities

- Move test files to lib/__tests__/ directory
- Extract formatting utilities (formatVersion, formatFileSize, formatDateTime)
  from fs-utils.ts to new utils.ts module
- Add Jest test configuration and test scripts
- Update component imports to use new utils module
- Add CLAUDE.md documentation for project structure

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

lib/fs-utils.ts

@@ -101,31 +101,3 @@ export async function getApks(project: string, version: string, commitId?: strin
   }
 }
 
-/**
- * 格式化版本号显示 (0_42 -> 0.42)
- */
-export function formatVersion(version: string): string {
-  return version.replace('_', '.');
-}
-
-/**
- * 格式化文件大小
- */
-export function formatFileSize(bytes: number): string {
-  if (bytes < 1024) return bytes + ' B';
-  if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(2) + ' KB';
-  if (bytes < 1024 * 1024 * 1024) return (bytes / (1024 * 1024)).toFixed(2) + ' MB';
-  return (bytes / (1024 * 1024 * 1024)).toFixed(2) + ' GB';
-}
-
-/**
- * 格式化日期时间
- */
-export function formatDateTime(date: Date): string {
-  const year = date.getFullYear();
-  const month = String(date.getMonth() + 1).padStart(2, '0');
-  const day = String(date.getDate()).padStart(2, '0');
-  const hours = String(date.getHours()).padStart(2, '0');
-  const minutes = String(date.getMinutes()).padStart(2, '0');
-  return `${year}-${month}-${day} ${hours}:${minutes}`;
-}