feat(due-date): NoteCard badge + edit + IPC

Inline 📅 YYYY-MM-DD badge appears in NoteCard between summary and
tags. Click to edit (HTML date input). Past dates: gray + line-through.
AI label shown when not user-edited (mirrors title/summary AI badge
policy). Empty state shows '📅 마감일 추가' link in gray.

New IPC inbox:setDueDate routes to NoteRepository.setDueDate which
sets due_date_edited_by_user=1 (per slice §1.1 invariant 2 — user
edit blocks future AI overwrite). Preload bridge + InboxApi type
extended.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/renderer/inbox/components/NoteCard.tsx

@@ -15,6 +15,93 @@ const aiBadgeStyle: React.CSSProperties = {
   background: '#eee', color: '#666', fontSize: 10, borderRadius: 3, verticalAlign: 'middle'
 };
 
+function isPastDue(iso: string, today: string): boolean {
+  return iso < today; // string comparison works for ISO YYYY-MM-DD
+}
+
+function todayKstIso(): string {
+  const KST_OFFSET_MS = 9 * 60 * 60 * 1000;
+  const k = new Date(Date.now() + KST_OFFSET_MS);
+  return k.toISOString().slice(0, 10);
+}
+
+function DueDateBadge({
+  value,
+  isEdited,
+  today,
+  onSave
+}: {
+  value: string | null;
+  isEdited: boolean;
+  today: string;
+  onSave: (next: string) => Promise<void>;
+}): React.ReactElement {
+  const [editing, setEditing] = useState(false);
+  const [draft, setDraft] = useState(value ?? '');
+
+  React.useEffect(() => { if (!editing) setDraft(value ?? ''); }, [value, editing]);
+
+  if (!editing) {
+    if (value === null) {
+      return (
+        <span
+          onClick={() => setEditing(true)}
+          style={{ fontSize: 11, color: '#bbb', cursor: 'pointer' }}
+          title="마감일 추가"
+        >
+          📅 마감일 추가
+        </span>
+      );
+    }
+    const past = isPastDue(value, today);
+    return (
+      <span style={{ fontSize: 11, display: 'inline-flex', alignItems: 'center', gap: 4 }}>
+        <span
+          onClick={() => setEditing(true)}
+          style={{
+            color: past ? '#999' : '#666',
+            textDecoration: past ? 'line-through' : 'none',
+            cursor: 'pointer'
+          }}
+          title={past ? '지난 마감일 — 클릭으로 편집' : '클릭으로 편집'}
+        >
+          📅 {value}
+        </span>
+        {!isEdited && (
+          <span
+            style={{
+              fontSize: 9, padding: '0 4px', background: '#eee',
+              color: '#888', borderRadius: 2
+            }}
+            title="AI 추출"
+          >
+            AI
+          </span>
+        )}
+      </span>
+    );
+  }
+
+  return (
+    <input
+      type="date"
+      value={draft}
+      onChange={(e) => setDraft(e.target.value)}
+      onBlur={async () => {
+        try { await onSave(draft); }
+        catch { /* keep editing if invalid */ return; }
+        setEditing(false);
+      }}
+      onKeyDown={(e) => {
+        if (e.key === 'Enter') (e.target as HTMLInputElement).blur();
+        if (e.key === 'Escape') { setDraft(value ?? ''); setEditing(false); }
+      }}
+      autoFocus
+      style={{ fontSize: 11, padding: 1 }}
+    />
+  );
+}
+
 export function NoteCard({ note, onDeleted, onUpdated }: Props): React.ReactElement {
   const [rawOpen, setRawOpen] = useState(note.aiStatus !== 'done');
   const [local, setLocal] = useState(note);
@@ -41,6 +128,17 @@ export function NoteCard({ note, onDeleted, onUpdated }: Props): React.ReactElem
     setLocal(updated); onUpdated(updated);
   }
 
+  async function saveDueDate(next: string) {
+    const value = next.trim() === '' ? null : next.trim();
+    // Light validation: empty or YYYY-MM-DD
+    if (value !== null && !/^\d{4}-\d{2}-\d{2}$/.test(value)) {
+      throw new Error('Invalid date');
+    }
+    await inboxApi.setDueDate(note.id, value);
+    const updated = { ...local, dueDate: value, dueDateEditedByUser: true };
+    setLocal(updated); onUpdated(updated);
+  }
+
   async function removeTag(tagName: string) {
     const next = local.tags.filter((t) => t.name !== tagName).map((t) => t.name);
     await inboxApi.updateAiFields(note.id, { tags: next });
@@ -102,6 +200,14 @@ export function NoteCard({ note, onDeleted, onUpdated }: Props): React.ReactElem
             />
             {!local.summaryEditedByUser && <span style={aiBadgeStyle} title="AI 제안">AI</span>}
           </div>
+          <div style={{ marginTop: 6 }}>
+            <DueDateBadge
+              value={local.dueDate}
+              isEdited={local.dueDateEditedByUser}
+              today={todayKstIso()}
+              onSave={saveDueDate}
+            />
+          </div>
           {local.tags.length > 0 && (
             <div style={{ marginTop: 8, display: 'flex', gap: 6, flexWrap: 'wrap' }}>
               {local.tags.map((t) => (