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/files.ts

@@ -8,6 +8,15 @@ import { AppError } from '../middleware/errorHandler';
 
 const router = Router();
 
+/** multer가 latin1로 전달하는 한글 파일명 복원 */
+function fixOriginalName(name: string): string {
+  try {
+    return Buffer.from(name, 'latin1').toString('utf8') || name;
+  } catch {
+    return name;
+  }
+}
+
 // POST /api/files/upload/:taskId  — 파일 업로드
 router.post('/upload/:taskId', upload.single('file'), async (req, res, next) => {
   try {
@@ -29,12 +38,17 @@ router.post('/upload/:taskId', upload.single('file'), async (req, res, next) =>
 
     const uploadedBy = await resolveTaskActorId(taskId);
 
+    const displayName = body.displayName?.trim() || null;
+    const sortOrder = body.sortOrder !== undefined ? Number(body.sortOrder) : 0;
+
     const fileRecord = await prisma.file.create({
       data: {
         taskId,
         milestoneId,
         filename: req.file.filename,
-        originalName: req.file.originalname,
+        originalName: fixOriginalName(req.file.originalname),
+        displayName,
+        sortOrder: Number.isNaN(sortOrder) ? 0 : sortOrder,
         mimetype: req.file.mimetype,
         size: req.file.size,
         path: req.file.path,
@@ -77,6 +91,56 @@ router.get('/:id/download', async (req, res, next) => {
   }
 });
 
+// POST /api/files/:id/replace  — 파일 교체
+router.post('/:id/replace', upload.single('file'), async (req, res, next) => {
+  try {
+    if (!req.file) throw new AppError(400, '파일이 없습니다.');
+
+    const existing = await prisma.file.findUnique({ where: { id: req.params.id } });
+    if (!existing) throw new AppError(404, '파일을 찾을 수 없습니다.');
+
+    if (fs.existsSync(existing.path)) {
+      fs.unlinkSync(existing.path);
+    }
+
+    const file = await prisma.file.update({
+      where: { id: req.params.id },
+      data: {
+        filename: req.file.filename,
+        originalName: fixOriginalName(req.file.originalname),
+        mimetype: req.file.mimetype,
+        size: req.file.size,
+        path: req.file.path,
+      },
+    });
+
+    res.json(file);
+  } catch (err) {
+    next(err);
+  }
+});
+
+// PATCH /api/files/:id  — 표시명·순서 수정
+router.patch('/:id', async (req, res, next) => {
+  try {
+    const { displayName, sortOrder } = req.body as { displayName?: string; sortOrder?: number };
+    const existing = await prisma.file.findUnique({ where: { id: req.params.id } });
+    if (!existing) throw new AppError(404, '파일을 찾을 수 없습니다.');
+
+    const file = await prisma.file.update({
+      where: { id: req.params.id },
+      data: {
+        ...(displayName !== undefined && { displayName: displayName?.trim() || null }),
+        ...(sortOrder !== undefined && { sortOrder: Number(sortOrder) }),
+      },
+    });
+
+    res.json(file);
+  } catch (err) {
+    next(err);
+  }
+});
+
 // DELETE /api/files/:id  — 파일 삭제
 router.delete('/:id', async (req, res, next) => {
   try {