feat(turnero): add chat plantillas API endpoints

- chat_get_plantillas.php: GET — returns enabled templates from
  turnero_chat_plantillas JOIN message_templates; auto-creates table
- chat_save_plantillas.php: POST {ids:[...]} — replaces all rows in
  turnero_chat_plantillas using DELETE + INSERT IGNORE in a transaction

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/turnero/api/chat_get_plantillas.php

@@ -0,0 +1,30 @@
+<?php
+/**
+ * GET — Plantillas habilitadas para el chat turnero.
+ * Crea la tabla si no existe aún.
+ */
+require_once __DIR__ . '/../../../config/config.php';
+requireAuthentication();
+header('Content-Type: application/json; charset=utf-8');
+
+try {
+    $pdo = Database::getInstance()->getConnection();
+
+    $pdo->exec("CREATE TABLE IF NOT EXISTS turnero_chat_plantillas (
+        template_id INT NOT NULL,
+        PRIMARY KEY (template_id)
+    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4");
+
+    $rows = $pdo->query(
+        "SELECT t.id, t.name, t.template_name, t.language_code, t.body_text,
+                t.header_text, t.header_type, t.footer_text, t.example_parameters, t.status
+           FROM turnero_chat_plantillas p
+           JOIN message_templates t ON t.id = p.template_id
+          ORDER BY t.name ASC"
+    )->fetchAll(PDO::FETCH_ASSOC);
+
+    echo json_encode(['ok' => true, 'data' => $rows]);
+} catch (Throwable $e) {
+    http_response_code(500);
+    echo json_encode(['ok' => false, 'error' => $e->getMessage()]);
+}

modules/turnero/api/chat_save_plantillas.php

@@ -0,0 +1,42 @@
+<?php
+/**
+ * POST — Guarda la lista de plantillas habilitadas para el chat turnero.
+ * Body: { ids: [1, 2, 3] }
+ */
+require_once __DIR__ . '/../../../config/config.php';
+requireAuthentication();
+header('Content-Type: application/json; charset=utf-8');
+
+if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
+    http_response_code(405);
+    echo json_encode(['ok' => false, 'error' => 'Método no permitido']);
+    exit;
+}
+
+try {
+    $input = json_decode(file_get_contents('php://input'), true) ?: [];
+    $ids   = array_map('intval', $input['ids'] ?? []);
+
+    $pdo = Database::getInstance()->getConnection();
+
+    $pdo->exec("CREATE TABLE IF NOT EXISTS turnero_chat_plantillas (
+        template_id INT NOT NULL,
+        PRIMARY KEY (template_id)
+    ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4");
+
+    $pdo->beginTransaction();
+    $pdo->exec("DELETE FROM turnero_chat_plantillas");
+
+    if (!empty($ids)) {
+        $ph   = implode(',', array_fill(0, count($ids), '(?)'));
+        $stmt = $pdo->prepare("INSERT IGNORE INTO turnero_chat_plantillas (template_id) VALUES $ph");
+        $stmt->execute($ids);
+    }
+
+    $pdo->commit();
+    echo json_encode(['ok' => true]);
+} catch (Throwable $e) {
+    if (isset($pdo) && $pdo->inTransaction()) $pdo->rollBack();
+    http_response_code(500);
+    echo json_encode(['ok' => false, 'error' => $e->getMessage()]);
+}