feat: detail page attachments, preview, and file metadata

Add file displayName/sortOrder APIs, result preview with Excel/video support,
unified attachment/link editing, feedback modal, and AuthProvider fix.
Run prisma migrate deploy on Render builds.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/routes/details.ts

@@ -0,0 +1,82 @@
+import { Router } from 'express';
+import { prisma } from '../lib/prisma';
+import { resolveTaskActorId } from '../lib/resolveUser';
+import { AppError } from '../middleware/errorHandler';
+
+const router = Router();
+
+async function resolveAuthorId(taskId: string, authorName?: string): Promise<string> {
+  const name = authorName?.toString().trim();
+  if (name) {
+    const user = await prisma.user.findFirst({ where: { name } });
+    if (user) return user.id;
+  }
+  return resolveTaskActorId(taskId);
+}
+
+// POST /api/details/:taskId
+router.post('/:taskId', async (req, res, next) => {
+  try {
+    const taskId = req.params.taskId;
+    const { content, milestoneId, authorName } = req.body as Record<string, string>;
+
+    if (!content?.toString().trim()) throw new AppError(400, '피드백 내용은 필수입니다.');
+
+    const task = await prisma.task.findUnique({ where: { id: taskId }, select: { id: true } });
+    if (!task) throw new AppError(404, '업무를 찾을 수 없습니다.');
+
+    if (milestoneId) {
+      const ms = await prisma.milestone.findFirst({ where: { id: milestoneId, taskId } });
+      if (!ms) throw new AppError(400, '유효하지 않은 업무 단계입니다.');
+    }
+
+    const updatedBy = await resolveAuthorId(taskId, authorName);
+
+    const detail = await prisma.taskDetail.create({
+      data: {
+        taskId,
+        milestoneId: milestoneId || null,
+        content: content.toString().trim(),
+        updatedBy,
+      },
+      include: { author: { select: { id: true, name: true } } },
+    });
+
+    res.status(201).json(detail);
+  } catch (err) {
+    next(err);
+  }
+});
+
+// PATCH /api/details/item/:id
+router.patch('/item/:id', async (req, res, next) => {
+  try {
+    const { content } = req.body as Record<string, string>;
+    if (!content?.toString().trim()) throw new AppError(400, '피드백 내용은 필수입니다.');
+
+    const existing = await prisma.taskDetail.findUnique({ where: { id: req.params.id } });
+    if (!existing) throw new AppError(404, '피드백을 찾을 수 없습니다.');
+
+    const detail = await prisma.taskDetail.update({
+      where: { id: req.params.id },
+      data: { content: content.toString().trim() },
+      include: { author: { select: { id: true, name: true } } },
+    });
+
+    res.json(detail);
+  } catch (err) {
+    next(err);
+  }
+});
+
+// DELETE /api/details/item/:id
+router.delete('/item/:id', async (req, res, next) => {
+  try {
+    await prisma.taskDetail.delete({ where: { id: req.params.id } });
+    res.status(204).send();
+  } catch (err) {
+    next(err);
+  }
+});
+
+export default router;