feat(collab): redesign note collaboration with REST auto-save, opt-in live session, and block locking

frontend/src/lib/api.ts

@@ -6,6 +6,9 @@ import {
   DocumentBlock,
   DocShare,
   DocLockInfo,
+  BlockLockInfo,
+  LiveSessionInfo,
+  DocLocksResponse,
   KanbanColumn,
   ListItem,
   ListShare,
@@ -625,6 +628,39 @@ export const api = {
     await request(`/api/v1/documents/${id}`, { method: 'DELETE' });
   },
 
+  async getDocLocks(docId: string): Promise<DocLocksResponse> {
+    const res = await request<DocLocksResponse>(`/api/v1/documents/${docId}/locks`);
+    return {
+      liveSession: res.liveSession || null,
+      blockLocks: ensureArray(res.blockLocks),
+    };
+  },
+
+  async lockBlock(docId: string, blockId: string, userColor?: string, ttlSeconds: number = 30): Promise<BlockLockInfo> {
+    return request<BlockLockInfo>(`/api/v1/documents/${docId}/blocks/${encodeURIComponent(blockId)}/lock`, {
+      method: 'POST',
+      body: JSON.stringify({ userColor, ttlSeconds }),
+    });
+  },
+
+  async unlockBlock(docId: string, blockId: string): Promise<{ status: string }> {
+    return request<{ status: string }>(`/api/v1/documents/${docId}/blocks/${encodeURIComponent(blockId)}/unlock`, {
+      method: 'POST',
+    });
+  },
+
+  async startLiveSession(docId: string): Promise<LiveSessionInfo> {
+    return request<LiveSessionInfo>(`/api/v1/documents/${docId}/live/start`, {
+      method: 'POST',
+    });
+  },
+
+  async endLiveSession(docId: string): Promise<{ status: string }> {
+    return request<{ status: string }>(`/api/v1/documents/${docId}/live/end`, {
+      method: 'POST',
+    });
+  },
+
   async moveDocument(id: string, folderPath: string): Promise<Document> {
     const d = await request<Document>(`/api/v1/documents/${id}/move`, {
       method: 'PUT',