Sync 1: revision + tombstone schema (M8 sync hub foundation)

The delta-sync substrate for the local-first native clients (Tauri,
Android). No API behavior change — pure infrastructure; triggers are
operator-verified on deploy (no Postgres CI lane).

Migration 0015:
- CREATE SEQUENCE sync_revision_seq.
- notes + labels gain sync_revision (bigint) + purged_at (tombstone),
  with existing rows backfilled to distinct increasing revisions.
- Trigger ts_set_sync_revision() BEFORE INSERT OR UPDATE on notes+labels
  stamps a fresh monotonic revision from the sequence, so no mutation
  site can forget to bump it (robustness over app-level bumps).
- Trigger ts_bump_parent_note_revision() AFTER INS/UPD/DEL on note_items,
  note_attachments, note_labels re-bumps the parent note, since a note
  syncs as a whole (items/labels/attachments travel inline).
- Indexes (owner_id, sync_revision) on notes + labels for the delta pull
  WHERE sync_revision > cursor.

purged_at is the hard-delete tombstone (distinct from deleted_at = trash)
so an offline client learns a row is gone instead of resurrecting it.
Model columns added to Note + Label (nullable; trigger populates them).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

src/thoughtsync/models/label.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import uuid
 from datetime import datetime
 
-from sqlalchemy import Boolean, DateTime, ForeignKey, Text, UniqueConstraint, func
+from sqlalchemy import BigInteger, Boolean, DateTime, ForeignKey, Text, UniqueConstraint, func
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -21,6 +21,11 @@ class Label(Base):
     name: Mapped[str] = mapped_column(Text(), nullable=False)
     color: Mapped[str] = mapped_column(Text(), nullable=False, default="default", server_default="default")
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False, server_default=func.now())
+    # Sync (M8): monotonic per-row revision (from sync_revision_seq via DB trigger) so a
+    # label rename/recolor/merge/delete propagates to native clients independently of notes.
+    sync_revision: Mapped[int | None] = mapped_column(BigInteger(), nullable=True)
+    # Hard-delete tombstone (content-less) so a deleted label is removed on clients.
+    purged_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
 
 
 class NoteLabel(Base):

src/thoughtsync/models/note.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import uuid
 from datetime import datetime
 
-from sqlalchemy import Boolean, DateTime, ForeignKey, Index, Integer, Text, func
+from sqlalchemy import BigInteger, Boolean, DateTime, ForeignKey, Index, Integer, Text, func
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import Mapped, mapped_column
 
@@ -59,6 +59,13 @@ class Note(Base):
     updated_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), nullable=False, server_default=func.now(), onupdate=func.now()
     )
+    # Sync (M8): a monotonic per-row revision drawn from sync_revision_seq and assigned
+    # by a DB trigger on every insert/update — the delta cursor native clients pull
+    # against. Nullable in the ORM because the trigger populates it server-side.
+    sync_revision: Mapped[int | None] = mapped_column(BigInteger(), nullable=True)
+    # Hard-delete tombstone: non-null => permanently deleted (content cleared), kept so
+    # offline clients learn the row is gone. Distinct from deleted_at (= recoverable trash).
+    purged_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True)
 
     def serialize(self) -> dict:
         return {