feat(persistence): PostgreSQL assistant store, chat persist fixes, gateway scripts

- Add SQLAlchemy Core repos, pg adapter/compat, assistant_store factory, Alembic bootstrap and migration/cutover scripts.

- Harden chat_message writes (NUL scrub for PG), turn_uuid on attempt failure, WS turn_runner fallbacks and gateway executed_turn_uuid init.

- start_gateway: log paths, PS7 stderr handling via cmd, background stdout/stderr redirect; runtime assistant_runtime_log_dir export.

- Ops: clear_all_chat_sessions with PG-only --postgresql and env-gated wipe; clear_postgres_chat_sessions.ps1.

- Tests: SA repos, pg compat, persist fallback, smoke env isolation; CI and docs touch-ups.

Co-authored-by: Cursor <cursoragent@cursor.com>

runtime/operations/scripts/unbind_wecom_bot.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 from svc.config.paths import db_path
 from svc.persistence.sqlite_store import SqliteStore
+from svc.persistence.assistant_store import get_assistant_store
 
 
 _CLEAR_KEYS = [
@@ -24,7 +25,7 @@ _CLEAR_KEYS = [
 
 
 def main() -> int:
-    store = SqliteStore(db_path())
+    store = get_assistant_store()
     with store._connect() as conn:  # internal cleanup script; safe to use store connection helper
         cur_ident = conn.execute("DELETE FROM channel_identity WHERE channel = ?", ("wecom",))
         ident_deleted = int(cur_ident.rowcount or 0)