fix: use proper logger in ConfigManager backup/restore methods

Replace console.log/console.error with proper logger usage in
backupEnvFile and restoreBackup methods. Use the existing 'log' logger
created with createLogger('ConfigManager') following the same pattern
used in other methods.

Changes:
- Import createLogger and create log instance
- Replace console.log with log.debug in backupEnvFile
- Replace console.error with log.error in both methods
- Pass error and path metadata as objects for structured logging
- Fix test to use correct backup path (process.cwd() + src/main/.env.backup)

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

tests/main/services/config/config-manager.test.ts

@@ -78,10 +78,10 @@ describe('ConfigManager - backup and restore', () => {
 
     expect(backupSuccess).toBe(true)
 
-    // Check backup file exists (in same location as .env file)
+    // Check backup file exists (in same location as .env file, which is src/main/)
     const fs = await import('fs')
     const path = await import('path')
-    const backupPath = path.resolve('src/main/.env.backup')
+    const backupPath = path.resolve(process.cwd(), 'src/main/.env.backup')
 
     expect(fs.existsSync(backupPath)).toBe(true)
   })