Fix TypeScript linting error in zipFileService

Remove unused filename parameter from filter function to resolve
@typescript-eslint/no-unused-vars error. Also include spotless
formatting changes.

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

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

app/core/src/main/java/stirling/software/SPDF/controller/api/MergeController.java

@@ -238,10 +238,10 @@ public class MergeController {
                     }
                 }
 
-                String payload = String.format(
+                String payload =
+                        String.format(
                                 "{\"errorFileIds\":%s,\"message\":\"Some of the selected files can't be merged\"}",
-                    errorFileIds.toString()
-                );
+                                errorFileIds.toString());
 
                 return ResponseEntity.status(HttpStatus.UNPROCESSABLE_ENTITY)
                         .header("Content-Type", MediaType.APPLICATION_JSON_VALUE)

frontend/src/services/zipFileService.ts

@@ -360,7 +360,7 @@ export class ZipFileService {
       const zipContents = await zip.loadAsync(file);
 
       // Get all files (not directories)
-      const allFiles = Object.entries(zipContents.files).filter(([filename, zipEntry]) =>
+      const allFiles = Object.entries(zipContents.files).filter(([, zipEntry]) =>
         !zipEntry.dir
       );