Put the reply text inside question notification emails

The notification only said that the school had answered and linked into
the LMS, so a student had to log in to read two lines. Delivered mail
plus an unread thread was the common outcome — one such thread was a
pre-sale question that never converted.

The mail now carries the answer itself (capped at 2000 chars, with a
pointer to the thread when longer or when files are attached). Quoted
blocks are HTML-escaped, which they were not before.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/app/api/questions/[id]/messages/route.ts

@@ -78,6 +78,8 @@ export async function POST(
       question.user.name,
       question.title,
       id,
+      text.trim(),
+      Boolean(safeFiles?.length),
     );
   } else {
     const staff = await prisma.user.findMany({

src/lib/email.ts

@@ -89,11 +89,19 @@ function btn(href: string, label: string) {
   </table>`;
 }
 
+function escapeHtml(text: string) {
+  return text
+    .replace(/&/g, "&amp;")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;");
+}
+
 function quote(text: string) {
   return `<table role="presentation" cellpadding="0" cellspacing="0" border="0" width="100%" style="margin:16px 0;">
     <tr>
       <td style="border-left:3px solid #323232;padding:10px 14px;background-color:#E8F0D8;">
-        <p style="margin:0;font-family:'Courier New',Courier,monospace;font-size:13px;line-height:1.6;color:#323232;">${text.replace(/\n/g, "<br/>")}</p>
+        <p style="margin:0;font-family:'Courier New',Courier,monospace;font-size:13px;line-height:1.6;color:#323232;">${escapeHtml(text).replace(/\n/g, "<br/>")}</p>
       </td>
     </tr>
   </table>`;
@@ -335,23 +343,39 @@ export async function sendQuestionCreatedEmail(
   }).catch((e) => console.error("[email] sendQuestionCreatedEmail:", e));
 }
 
+// Текст ответа кладём прямо в письмо: раньше письмо звало в LMS «прочитать ответ»,
+// и ради двух строк человеку надо было авторизоваться — часть студентов так и не
+// открывала тред (isRead=false при доставленном письме).
+const REPLY_PREVIEW_LIMIT = 2000;
+
 export async function sendQuestionReplyEmail(
   to: string,
   studentName: string,
   questionTitle: string,
   questionId: string,
+  replyText: string,
+  hasFiles = false,
 ) {
   const school = await getSchoolName();
+  const trimmed = replyText.trim();
+  const preview =
+    trimmed.length > REPLY_PREVIEW_LIMIT
+      ? `${trimmed.slice(0, REPLY_PREVIEW_LIMIT)}…`
+      : trimmed;
+  const truncated = trimmed.length > REPLY_PREVIEW_LIMIT;
+
   await getResend().emails.send({
     from: FROM,
     to,
     subject: `Ответ на ваш вопрос`,
     html: base(`
       <p ${p}>Привет, ${studentName}!</p>
-      <p ${p}>Школа ответила на ваш вопрос:</p>
-      ${quote(questionTitle)}
-      <p ${pLast}>Откройте тред чтобы прочитать ответ:</p>
-      ${btn(`${BASE_URL}/questions/${questionId}`, "Читать ответ")}
+      <p ${p}>Школа ответила на ваш вопрос «${escapeHtml(questionTitle)}»:</p>
+      ${quote(preview)}
+      ${truncated ? `<p ${p}>Ответ длинный — целиком он в треде.</p>` : ""}
+      ${hasFiles ? `<p ${p}>К ответу приложены файлы — открыть их можно в треде.</p>` : ""}
+      <p ${pLast}>Ответить или посмотреть переписку целиком:</p>
+      ${btn(`${BASE_URL}/questions/${questionId}`, "Открыть тред")}
     `, school),
   }).catch((e) => console.error("[email] sendQuestionReplyEmail:", e));
 }