feat(expo): add chat message and WebSocket event types

xtablo-expo/types/chat.types.ts

@@ -0,0 +1,39 @@
+export interface ChatMessage {
+  id: string;
+  userId: string;
+  text: string;
+  createdAt: string;
+  clientId: string;
+  /** True while the message is only local (not yet echoed by server). */
+  optimistic?: boolean;
+}
+
+/** Raw shape returned by the REST API (snake_case from Postgres). */
+export interface RawApiMessage {
+  id: string;
+  user_id: string;
+  text: string;
+  created_at: string;
+  client_id?: string;
+}
+
+export type ServerMessage =
+  | { type: "message.new"; id: string; userId: string; text: string; createdAt: string; clientId: string }
+  | { type: "typing"; userId: string; isTyping: boolean }
+  | { type: "presence.update"; userId: string; status: "online" | "offline" }
+  | { type: "error"; code: string; message: string };
+
+export interface UnreadCount {
+  channel_id: string;
+  unread_count: number;
+}
+
+export function normalizeMessage(raw: RawApiMessage): ChatMessage {
+  return {
+    id: raw.id,
+    userId: raw.user_id,
+    text: raw.text,
+    createdAt: raw.created_at,
+    clientId: raw.client_id ?? "",
+  };
+}