Add InquiryFollowup model

Introduce a new InquiryFollowup model with helper methods for managing follow-ups. Implements create() to insert records (with type casts/defaults) and return the new ID, latestForInquiry() to fetch recent follow-ups joined with admin info (ordered by created_at and id, with a limit), and countOpenByAssignee() to count incomplete follow-ups for a given assigned admin. Uses Database::connection() with prepared statements and basic input validation.

Author: coowinit

app/Models/InquiryFollowup.php

@@ -0,0 +1,80 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Models;
+
+use App\Core\Database;
+use PDO;
+
+final class InquiryFollowup
+{
+    public function create(array $data): int
+    {
+        $sql = 'INSERT INTO inquiry_followups (
+                    inquiry_id,
+                    admin_id,
+                    followup_type,
+                    content,
+                    next_contact_at,
+                    is_completed
+                ) VALUES (
+                    :inquiry_id,
+                    :admin_id,
+                    :followup_type,
+                    :content,
+                    :next_contact_at,
+                    :is_completed
+                )';
+
+        $stmt = Database::connection()->prepare($sql);
+        $ok = $stmt->execute([
+            'inquiry_id' => (int) ($data['inquiry_id'] ?? 0),
+            'admin_id' => isset($data['admin_id']) && $data['admin_id'] !== '' ? (int) $data['admin_id'] : null,
+            'followup_type' => (string) ($data['followup_type'] ?? 'note'),
+            'content' => (string) ($data['content'] ?? ''),
+            'next_contact_at' => $data['next_contact_at'] ?? null,
+            'is_completed' => !empty($data['is_completed']) ? 1 : 0,
+        ]);
+
+        return $ok ? (int) Database::connection()->lastInsertId() : 0;
+    }
+
+    public function latestForInquiry(int $inquiryId, int $limit = 20): array
+    {
+        $sql = 'SELECT
+                    f.*,
+                    a.username AS admin_username,
+                    a.nickname AS admin_nickname
+                FROM inquiry_followups f
+                LEFT JOIN admins a ON a.id = f.admin_id
+                WHERE f.inquiry_id = :inquiry_id
+                ORDER BY f.created_at DESC, f.id DESC
+                LIMIT :limit';
+
+        $stmt = Database::connection()->prepare($sql);
+        $stmt->bindValue(':inquiry_id', $inquiryId, PDO::PARAM_INT);
+        $stmt->bindValue(':limit', max(1, $limit), PDO::PARAM_INT);
+        $stmt->execute();
+
+        return $stmt->fetchAll();
+    }
+
+    public function countOpenByAssignee(int $adminId): int
+    {
+        if ($adminId <= 0) {
+            return 0;
+        }
+
+        $sql = 'SELECT COUNT(*)
+                FROM inquiry_followups f
+                INNER JOIN inquiries i ON i.id = f.inquiry_id
+                WHERE i.assigned_admin_id = :admin_id
+                  AND f.is_completed = 0';
+
+        $stmt = Database::connection()->prepare($sql);
+        $stmt->execute(['admin_id' => $adminId]);
+
+        return (int) $stmt->fetchColumn();
+    }
+}