fix: stage save errors and add milestone progress field

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

frontend/src/components/detail/StageModal.tsx

@@ -6,6 +6,7 @@ export interface StageFormData {
   title: string;
   startDate: string;
   dueDate: string;
+  progress: number;
   description: string;
   feedback: string;
   links: MilestoneLink[];
@@ -39,6 +40,7 @@ export function StageModal({ mode, milestone, onSave, onClose, saving }: StageMo
     title: milestone?.title ?? '',
     startDate: toDateInput(milestone?.startDate),
     dueDate: toDateInput(milestone?.dueDate),
+    progress: milestone?.progress ?? 0,
     description: milestone?.description ?? '',
     feedback: '',
     links: parseLinks(milestone?.links),
@@ -92,6 +94,22 @@ export function StageModal({ mode, milestone, onSave, onClose, saving }: StageMo
             />
           </label>
 
+          <label className="block">
+            <span className="mb-1 flex items-center justify-between text-sm font-bold text-slate-500">
+              <span>진행률</span>
+              <span className="text-lg font-black text-emerald-600">{form.progress}%</span>
+            </span>
+            <input
+              type="range"
+              min={0}
+              max={100}
+              step={5}
+              value={form.progress}
+              onChange={(e) => set('progress', Number(e.target.value))}
+              className="w-full accent-emerald-600"
+            />
+          </label>
+
           <div className="grid grid-cols-2 gap-3">
             <label className="block">
               <span className="mb-1 block text-sm font-bold text-slate-500">시작일</span>

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);
     }

frontend/src/types/index.ts

@@ -86,6 +86,7 @@ export interface Milestone {
   description: string | null;
   startDate: string | null;
   dueDate: string | null;
+  progress: number;
   links: string | null;
   completedAt: string | null;
   order: number;