refactor: add return type hints to all controller methods

Added proper return types (View, RedirectResponse, JsonResponse, Collection)
to 40+ controller methods across 16 controllers. Also added missing
imports for Illuminate response types and tightened parameter types
(e.g. InstallationController::showStep now uses int instead of mixed).

app/Http/Controllers/Badge/BadgeController.php

@@ -3,12 +3,14 @@
 namespace App\Http\Controllers\Badge;
 
 use App\Http\Controllers\Controller;
+use Illuminate\Http\RedirectResponse;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Auth;
+use Illuminate\View\View;
 
 class BadgeController extends Controller
 {
-    public function show()
+    public function show(): View
     {
         $cost = 150;
         $currencyType = 'credits';
@@ -50,7 +52,7 @@ class BadgeController extends Controller
         return view('draw-badge', ['cost' => $cost, 'currencyType' => $currencyType, 'folderError' => $folderError, 'errorMessage' => $errorMessage]);
     }
 
-    public function buy(Request $request)
+    public function buy(Request $request): RedirectResponse
     {
         $user = Auth::user();