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/Models/ClientCategory.php

@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Support\Str;
+
+class ClientCategory extends Model
+{
+    protected $fillable = [
+        'name', 'slug', 'parent_id', 'icon', 'color',
+        'description', 'is_system', 'sort_order',
+    ];
+
+    protected $casts = [
+        'is_system'  => 'boolean',
+        'sort_order' => 'integer',
+    ];
+
+    // ── Relationships ────────────────────────────────────────────
+
+    public function parent(): BelongsTo
+    {
+        return $this->belongsTo(ClientCategory::class, 'parent_id');
+    }
+
+    public function children(): HasMany
+    {
+        return $this->hasMany(ClientCategory::class, 'parent_id')->orderBy('sort_order');
+    }
+
+    public function clients(): HasMany
+    {
+        return $this->hasMany(Client::class, 'category_id');
+    }
+
+    // ── Scopes ───────────────────────────────────────────────────
+
+    public function scopeRoots($query)
+    {
+        return $query->whereNull('parent_id')->orderBy('sort_order');
+    }
+
+    public function scopeTopLevel($query)
+    {
+        return $query->whereNull('parent_id');
+    }
+
+    // ── Accessors ────────────────────────────────────────────────
+
+    public function getFullNameAttribute(): string
+    {
+        return $this->parent
+            ? $this->parent->name . ' › ' . $this->name
+            : $this->name;
+    }
+
+    // ── Events ───────────────────────────────────────────────────
+
+    protected static function boot(): void
+    {
+        parent::boot();
+
+        static::creating(function (ClientCategory $cat): void {
+            if (empty($cat->slug)) {
+                $cat->slug = Str::slug($cat->name);
+            }
+        });
+    }
+}