docs(map): cross-device sync rewrite, fixed defects and what is still local

docs/map/09-supabase-backend.md

@@ -19,6 +19,7 @@
 | Core schema + RLS + auth triggers | initial tables, profiles, triggers |
 | Storage buckets | audio, meeting documents, exports |
 | Teams | team invites, membership, roles, `team_activities` feed (`20260913000033`) |
+| Cross-device sync | `20260927000034`: `sync_tombstones` (AFTER DELETE triggers on 8 synced tables, owner-read RLS, realtime, `prune_sync_tombstones_v1`), `history.revision` bump on content change, `meeting_memos.updated_at`, `(user_id, updated_at, id)` cursor indexes, client-keyed `sync_upsert/delete_user_template_v1`, realtime for `devices`/`memo_tags`/`custom_instructions`/`user_templates`, and `export_account_portability` projected back onto v1 archive keys |
 | Knowledge / RAG | `knowledge_documents`, `knowledge_chunks`, pgvector |
 | Notifications / push | push tokens, durable outbox |
 | Billing | Payple, subscriptions, payment provider events/operations (`'stripe'` provider values kept only for historical rows) |
@@ -78,7 +79,8 @@ Canonical product data lives in Supabase Postgres with RLS:
 - **Content:** `history`, `meetings`, `meeting_memos`, `meeting_documents`, `memos`, `dictionary`, `commands`/instructions, `templates`.
 - **Knowledge:** `knowledge_documents`, `knowledge_chunks` (pgvector).
 - **Teams:** teams, members, invites, activity feed (`team_activities`, RPC-only writes, realtime-enabled).
-- **Delivery:** `devices`, `push_tokens`, push outbox.
+- **Delivery:** `devices` (mobile + desktop `windows`/`macos`), `push_tokens`, push outbox.
+- **Sync:** `sync_tombstones` — deletion log the desktop mirror (and any offline client) reads by cursor.
 - **Monetization:** `subscriptions`, `payment_provider_events/operations`, `ad_reward_claims`, IAP receipts, generation receipts.
 - **Ops:** `audit_log` + admin operation records.
 - **Portability:** `portable_exports` (+ storage).