fix: remove 9 unused variables across multiple files

Fixed unused variables in:
- database-file-encryption.ts: removed currentFingerprint (backend)
- FileManagerContextMenu.tsx: removed ExternalLink import, hasDirectories
- frontend-logger.ts: removed 5 unused shortUrl variables

Continued reducing lint errors

src/backend/utils/database-file-encryption.ts

@@ -301,7 +301,6 @@ class DatabaseFileEncryption {
       const metadata: EncryptedFileMetadata = JSON.parse(metadataContent);
 
       const fileStats = fs.statSync(encryptedPath);
-      const currentFingerprint = "termix-v1-file";
 
       return {
         version: metadata.version,