feat: add validation for minimum length on various fields and update type definitions

backend/app/schemas/gateway_api.py

@@ -0,0 +1,47 @@
+from __future__ import annotations
+
+from sqlmodel import SQLModel
+
+from app.schemas.common import NonEmptyStr
+
+
+class GatewaySessionMessageRequest(SQLModel):
+    content: NonEmptyStr
+
+
+class GatewayResolveQuery(SQLModel):
+    board_id: str | None = None
+    gateway_url: str | None = None
+    gateway_token: str | None = None
+    gateway_main_session_key: str | None = None
+
+
+class GatewaysStatusResponse(SQLModel):
+    connected: bool
+    gateway_url: str
+    sessions_count: int | None = None
+    sessions: list[object] | None = None
+    main_session_key: str | None = None
+    main_session: object | None = None
+    main_session_error: str | None = None
+    error: str | None = None
+
+
+class GatewaySessionsResponse(SQLModel):
+    sessions: list[object]
+    main_session_key: str | None = None
+    main_session: object | None = None
+
+
+class GatewaySessionResponse(SQLModel):
+    session: object
+
+
+class GatewaySessionHistoryResponse(SQLModel):
+    history: list[object]
+
+
+class GatewayCommandsResponse(SQLModel):
+    protocol_version: int
+    methods: list[str]
+    events: list[str]