feat: add Memory Gateway integration with async support for memory snapshots and user management

app-instance/backend/beaver/memory/gateway/store.py

@@ -0,0 +1,54 @@
+"""SQLite cache for Memory Gateway user credentials."""
+
+from __future__ import annotations
+
+import sqlite3
+import time
+from pathlib import Path
+
+
+class MemoryGatewayUserStore:
+    """Persist `user_id -> user_key` mappings returned by Memory Gateway."""
+
+    def __init__(self, db_path: str | Path) -> None:
+        self.db_path = Path(db_path)
+        self.db_path.parent.mkdir(parents=True, exist_ok=True)
+        self._init_schema()
+
+    def get_user_key(self, user_id: str) -> str | None:
+        with self._connect() as conn:
+            row = conn.execute(
+                "SELECT user_key FROM memory_gateway_users WHERE user_id = ?",
+                (user_id,),
+            ).fetchone()
+        return str(row[0]) if row else None
+
+    def save_user_key(self, user_id: str, user_key: str) -> None:
+        now = time.time()
+        with self._connect() as conn:
+            conn.execute(
+                """
+                INSERT INTO memory_gateway_users (user_id, user_key, created_at, updated_at)
+                VALUES (?, ?, ?, ?)
+                ON CONFLICT(user_id) DO UPDATE SET
+                    user_key = excluded.user_key,
+                    updated_at = excluded.updated_at
+                """,
+                (user_id, user_key, now, now),
+            )
+
+    def _init_schema(self) -> None:
+        with self._connect() as conn:
+            conn.execute(
+                """
+                CREATE TABLE IF NOT EXISTS memory_gateway_users (
+                    user_id TEXT PRIMARY KEY,
+                    user_key TEXT NOT NULL,
+                    created_at REAL NOT NULL,
+                    updated_at REAL NOT NULL
+                )
+                """
+            )
+
+    def _connect(self) -> sqlite3.Connection:
+        return sqlite3.connect(str(self.db_path))