Extract config and types into separate files, clean up index.ts

- src/config.ts: configuration constants
- src/types.ts: TypeScript interfaces
- src/index.ts: remove section comments, streamline code

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/types.ts

@@ -0,0 +1,18 @@
+export interface RegisteredGroup {
+  name: string;
+  folder: string;
+  trigger: string;
+  added_at: string;
+}
+
+export interface Session {
+  [folder: string]: string;
+}
+
+export interface NewMessage {
+  id: string;
+  chat_jid: string;
+  sender: string;
+  content: string;
+  timestamp: string;
+}