fix: stage save errors and add milestone progress field

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

frontend/src/pages/DetailPage.tsx

@@ -49,7 +49,9 @@ function sortByIsoDesc<T>(items: T[], pick: (item: T) => string) {
 }
 
 function milestoneProgress(m: Milestone) {
-  return m.completedAt ? 100 : 0;
+  if (m.completedAt) return 100;
+  const p = m.progress ?? 0;
+  return Math.min(100, Math.max(0, p));
 }
 
 function parseContentLines(text: string | null | undefined) {
@@ -274,7 +276,6 @@ function DetailView({ task }: { task: TaskWithRelations }) {
       const form = new FormData();
       form.append('file', file);
       form.append('milestoneId', milestoneId);
-      form.append('uploadedBy', task.creatorId);
       await apiClient.post(`/files/upload/${task.id}`, form, {
         headers: { 'Content-Type': 'multipart/form-data' },
       });
@@ -289,21 +290,41 @@ function DetailView({ task }: { task: TaskWithRelations }) {
         description: data.description.trim() || undefined,
         startDate: data.startDate || undefined,
         dueDate: data.dueDate || undefined,
+        progress: data.progress,
         feedback: data.feedback.trim() || undefined,
-        links: JSON.stringify(data.links),
+        links: data.links.length > 0 ? JSON.stringify(data.links) : undefined,
       };
 
+      let milestoneId: string;
+
       if (stageModal?.mode === 'add') {
         const { data: created } = await apiClient.post<Milestone>(`/milestones/${task.id}`, payload);
-        if (fileList.length) await uploadFiles(created.id, fileList);
+        milestoneId = created.id;
         setSelectedId(created.id);
       } else if (stageModal?.milestone) {
-        await apiClient.patch(`/milestones/item/${stageModal.milestone.id}`, payload);
-        if (fileList.length) await uploadFiles(stageModal.milestone.id, fileList);
+        const { data: updated } = await apiClient.patch<Milestone>(
+          `/milestones/item/${stageModal.milestone.id}`,
+          payload,
+        );
+        milestoneId = updated.id;
+      } else {
+        return;
+      }
+
+      if (fileList.length > 0) {
+        try {
+          await uploadFiles(milestoneId, fileList);
+        } catch {
+          alert('단계는 저장됐지만 파일 업로드에 실패했습니다.');
+        }
       }
 
       await qc.invalidateQueries({ queryKey: ['task', task.id] });
       setStageModal(null);
+    } catch (err: unknown) {
+      const ax = err as { response?: { data?: { message?: string } }; message?: string };
+      const msg = ax.response?.data?.message || ax.message || '단계 저장에 실패했습니다.';
+      alert(msg);
     } finally {
       setStageSaving(false);
     }