Add PostgreSQL production backend to eliminate SQLite lock contention.

Support DATABASE_URL with connection pooling, pg_dump backups, SQLite migration script, and deploy_postgres.sh with docs.

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

risk/account_risk_lib.py

@@ -7,12 +7,13 @@
 from __future__ import annotations
 
 import os
-import sqlite3
 import time
 from datetime import datetime
 from typing import Any, Callable, Optional, TypeVar
 from zoneinfo import ZoneInfo
 
+from db_conn import OperationalError
+
 T = TypeVar("T")
 
 STATUS_NORMAL = "normal"
@@ -100,12 +101,13 @@ _SCHEMA_READY = False
 
 
 def _db_retry(action: Callable[[], T], *, retries: int = 8, base_delay: float = 0.03) -> T:
-    last: sqlite3.OperationalError | None = None
+    last: OperationalError | None = None
     for i in range(retries):
         try:
             return action()
-        except sqlite3.OperationalError as exc:
-            if "locked" not in str(exc).lower():
+        except OperationalError as exc:
+            msg = str(exc).lower()
+            if "locked" not in msg and "serialize" not in msg and "deadlock" not in msg:
                 raise
             last = exc
             time.sleep(base_delay * (2 ** i))