feat: add about page with versions, changelog, and how-to-play

- New GET /about API endpoint caches Gitea releases for 5 minutes
- AboutPanel displays client version (via Vite define), API version, collapsible changelog, and How to Play guide
- GiteaRelease and AboutResponse types added to shared package

apps/web/src/api/client.ts

@@ -1,4 +1,5 @@
 import type {
+  AboutResponse,
   AuthResponse,
   BossChallengeRequest,
   BossChallengeResponse,
@@ -45,6 +46,9 @@ const request = async <T>(
   return response.json() as Promise<T>;
 };
 
+export const getAbout = async (): Promise<AboutResponse> =>
+  request<AboutResponse>("/about");
+
 export const getAuthUrl = async (): Promise<string> => {
   const data = await request<{ url: string }>("/auth/url");
   return data.url;