Implement file upload and viewing functionality; refactor letter migrations and models to use UUIDs

app/Http/Controllers/FileViewController.php

@@ -0,0 +1,14 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\FileUpload;
+
+class FileViewController extends Controller
+{
+    public function show($id)
+    {
+        $file = FileUpload::findOrFail($id);
+        return response()->file(storage_path('app/public/' . $file->file_path));
+    }
+}