feat: Add notification services for Email, Telegram, and WhatsApp

- Implement EmailNotifier for sending batch and test notifications via email.
- Implement TelegramNotifier for sending batch and test notifications via Telegram.
- Implement WahaNotifier for sending batch and test notifications via WhatsApp using WAHA API.
- Create migration for client_categories table and update clients table to include category_id.
- Create migration for notification_settings table to manage notification configurations.
- Add ClientCategorySeeder to populate default client categories.
- Create manifest.json for PWA support.
- Implement service worker (sw.js) for caching static assets and offline support.
- Add edit event view for modifying scheduled events.
- Create search results view for displaying search queries.
- Develop notification settings view for configuring notification channels and triggers.

app/Services/Notifications/EmailNotifier.php

@@ -0,0 +1,43 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Services\Notifications;
+
+use App\Models\NotificationSetting;
+use Illuminate\Support\Facades\Mail;
+
+class EmailNotifier
+{
+    public function sendBatch(NotificationSetting $setting, array $messages): void
+    {
+        $toEmail = $setting->config['to_email'] ?? null;
+
+        if (! $toEmail) {
+            throw new \RuntimeException('Email to_email address is required.');
+        }
+
+        $combined = implode("\n\n---\n\n", $messages);
+
+        Mail::raw($combined, function ($mail) use ($toEmail, $setting): void {
+            $mail->to($toEmail)
+                 ->subject("🐱 KOL Manager — {$setting->name} Notifications");
+        });
+    }
+
+    public function sendTest(NotificationSetting $setting): void
+    {
+        $toEmail = $setting->config['to_email'] ?? null;
+
+        if (! $toEmail) {
+            throw new \RuntimeException('Email to_email address is required.');
+        }
+
+        Mail::raw(
+            "🐱 KOL Manager — Test Notification\n\nYour Email channel is configured correctly! 🎉",
+            function ($mail) use ($toEmail): void {
+                $mail->to($toEmail)->subject('🐱 KOL Manager — Test Notification');
+            }
+        );
+    }
+}