feat: Implement read cursor activity tracking and recent activity dashboard with context

app/Http/Controllers/DashboardController.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Services\ActivityService;
+use Illuminate\Http\Request;
+use Inertia\Inertia;
+
+class DashboardController extends Controller
+{
+    public function index(Request $request, ActivityService $activityService)
+    {
+        $user = $request->user();
+        $unreadEntities = $activityService->getUnreadEntitiesGrouped($user);
+
+        return Inertia::render('Dashboard', [
+            'unreadEntities' => $unreadEntities,
+        ]);
+    }
+}