Add AI chat feature

server/modules/chat/model.ts

@@ -0,0 +1,21 @@
+import { t, type UnwrapSchema } from "elysia";
+
+export const ChatModel = {
+  chat: t.Object({
+    messages: t.Array(
+      t.Object({
+        id: t.String(),
+        role: t.Union([
+          t.Literal("user"),
+          t.Literal("assistant"),
+          t.Literal("system"),
+        ]),
+        parts: t.Array(t.Any()),
+      }),
+    ),
+  }),
+} as const;
+
+export type ChatModel = {
+  [k in keyof typeof ChatModel]: UnwrapSchema<(typeof ChatModel)[k]>;
+};