implement chat messaging with event proposals

- Add functional chat with server communication and test responses
- Add ProposedEventCard component for confirm/reject actions
- Move Constants (Day, Month) from client to shared package
- Add dateHelpers utility for weekday calculations
- Extend Themes.tsx with button and text colors
- Update CLAUDE.md with current implementation status
- Add *.tsbuildinfo to .gitignore

apps/client/src/services/ApiClient.ts

@@ -1,5 +1,5 @@
 const API_BASE_URL =
-  process.env.EXPO_PUBLIC_API_URL || "http://localhost:3000/api";
+  process.env.EXPO_PUBLIC_API_URL || "http://localhost:3001/api";
 
 type HttpMethod = "GET" | "POST" | "PUT" | "DELETE";
 
@@ -9,11 +9,24 @@ interface RequestOptions {
 }
 
 async function request<T>(
-  _method: HttpMethod,
-  _endpoint: string,
-  _options?: RequestOptions,
+  method: HttpMethod,
+  endpoint: string,
+  options?: RequestOptions,
 ): Promise<T> {
-  throw new Error("Not implemented");
+  const response = await fetch(`${API_BASE_URL}${endpoint}`, {
+    method,
+    headers: {
+      "Content-Type": "application/json",
+      ...options?.headers,
+    },
+    body: options?.body ? JSON.stringify(options.body) : undefined,
+  });
+
+  if (!response.ok) {
+    throw new Error(`HTTP ${response.status}`);
+  }
+
+  return response.json();
 }
 
 export const ApiClient = {