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/Community/LeaderboardController.php

@@ -60,7 +60,7 @@ class LeaderboardController extends Controller
         ]);
     }
 
-    private function retrieveSettings($column)
+    private function retrieveSettings(string $column): \Illuminate\Database\Eloquent\Collection
     {
         return UserSetting::query()
             ->select(['user_id', $column])

app/Http/Controllers/Community/RadioLeaderboardController.php

@@ -9,10 +9,11 @@ use App\Models\User;
 use Carbon\Carbon;
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\DB;
+use Illuminate\View\View;
 
 class RadioLeaderboardController extends Controller
 {
-    public function __invoke(Request $request)
+    public function __invoke(Request $request): View
     {
         $period = $request->get('period', 'all');
 

app/Http/Controllers/Community/Staff/StaffApplicationsController.php

@@ -5,6 +5,7 @@ namespace App\Http\Controllers\Community\Staff;
 use App\Http\Controllers\Controller;
 use App\Models\Community\Staff\WebsiteOpenPosition;
 use App\Models\Community\Staff\WebsiteStaffApplications;
+use Illuminate\Http\RedirectResponse;
 use Illuminate\Http\Request;
 use Illuminate\View\View;
 
@@ -32,7 +33,7 @@ class StaffApplicationsController extends Controller
         return view('community.staff-apply', ['position' => $position]);
     }
 
-    public function store(Request $request, WebsiteOpenPosition $position)
+    public function store(Request $request, WebsiteOpenPosition $position): RedirectResponse
     {
         abort_unless($position->position_kind === 'rank', 404);
 

app/Http/Controllers/Community/Staff/WebsiteTeamApplicationsController.php

@@ -5,6 +5,7 @@ namespace App\Http\Controllers\Community\Staff;
 use App\Http\Controllers\Controller;
 use App\Models\Community\Staff\WebsiteOpenPosition;
 use App\Models\Community\Staff\WebsiteStaffApplications;
+use Illuminate\Http\RedirectResponse;
 use Illuminate\Http\Request;
 use Illuminate\View\View;
 
@@ -48,7 +49,7 @@ class WebsiteTeamApplicationsController extends Controller
         ]);
     }
 
-    public function store(Request $request, WebsiteOpenPosition $position)
+    public function store(Request $request, WebsiteOpenPosition $position): RedirectResponse
     {
         abort_unless($position->position_kind === 'team', 404);