feat(acadenice): add sync blocks for cross-page content sharing — R4.2
Implements Notion-style sync blocks: a Tiptap node whose content is shared
across N pages. Editing via the Hocuspocus overlay propagates to all instances
via Yjs collab + SSE broadcast (EventEmitter2 bus).
Server: DB migration, NestJS module (CRUD + BFS cycle detection + broadcast),
Hocuspocus persistence extension extended for sync-block-* docs, 3 new RBAC
permissions (sync_blocks:create/edit/delete), seeded to Admin/Editor/Member.
Client: SyncBlockExtension (Tiptap node), SyncBlockNodeView (NodeView +
Mantine Modal overlay + SSE hook), /sync-block slash command, service client.
Tests: 32 server Jest + 18 client Vitest, all green.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Corentin
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