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

app-instance/backend/beaver/foundation/config/schema.py

@@ -115,6 +115,26 @@ class BackendIdentityConfig:
     public_base_url: str = ""
 
 
+@dataclass(slots=True)
+class MemoryGatewayConfig:
+    """Memory Gateway integration settings."""
+
+    base_url: str = ""
+    api_key: str = ""
+    default_user_id: str = ""
+    timeout_seconds: float = 15.0
+    snapshot_search_limit: int = 5
+    commit_on_run_complete: bool = True
+
+
+@dataclass(slots=True)
+class MemoryConfig:
+    """Runtime memory strategy configuration."""
+
+    mode: str = "local"
+    gateway: MemoryGatewayConfig = field(default_factory=MemoryGatewayConfig)
+
+
 @dataclass(slots=True)
 class BeaverConfig:
     """Config loaded once per backend sandbox instance."""
@@ -126,6 +146,7 @@ class BeaverConfig:
     authz: AuthzConfig = field(default_factory=AuthzConfig)
     channels: dict[str, ChannelConfig] = field(default_factory=dict)
     backend_identity: BackendIdentityConfig = field(default_factory=BackendIdentityConfig)
+    memory: MemoryConfig = field(default_factory=MemoryConfig)
     config_path: Path | None = None
 
     @property