Update client to use /topics endpoint and add getVersion method

- Update listTopics() to use /topics endpoint instead of /
- Add getVersion() method to fetch server version information
- Add VersionResponse type and export it

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/types.ts

@@ -140,6 +140,14 @@ export interface PollAnswererResponse {
  */
 export type PollResponse = PollOffererResponse | PollAnswererResponse;
 
+/**
+ * Response from GET / - server version information
+ */
+export interface VersionResponse {
+  /** Git commit hash or version identifier */
+  version: string;
+}
+
 /**
  * Response from GET /health
  */