feat(desktop): two-way cloud sync with mobile and web

Rewrites the desktop mirror as services/sync/SyncEngine: a persistent
outbox, per-account server-clock keyset cursors with paging, pulls that never
overwrite unsent local edits, deletions both ways through sync_tombstones and
per-row failure isolation. It now covers history titles and favorites,
dictionary, every meeting's memos and documents, memo tags, user commands and
dictation/meeting templates, and registers the desktop as a device that the
phone can disconnect.

Fixes shipped defects: the first pull after sign-in fetched nothing, only
the first meeting's children were pushed, team meetings leaked into the
personal database and lost team_id on re-push, and Realtime never connected
because Electron's Node 20 has no global WebSocket (ws is now the transport).
Anonymous local-mode records are imported into the first account that signs
in. The settings sync section is translated and shows pending/rejected
changes; synced screens reload on app:dataChanged.

packages/core/src/ipc-channels.ts

@@ -145,6 +145,7 @@ export const IPC_CHANNELS = {
     GET_BY_ID: 'history:getById',
     DELETE: 'history:delete',
     DELETE_ALL: 'history:deleteAll',
+    SET_FAVORITE: 'history:setFavorite',
     SEARCH: 'history:search',
     EXPORT: 'history:export',
     // Main → Renderer events