style: auto-fix ESLint issues (curly braces and formatting)

- Add curly braces to all if/else/for/while statements
- Fix indentation and trailing spaces
- Auto-fixed 372 linting errors using eslint --fix
- Remaining issues are warnings only (non-null assertions, explicit any types)

src/gateway/handlers/sessions.ts

@@ -16,7 +16,7 @@ export function createSessionHandlers(deps: SessionHandlerDeps) {
         id,
         messageCount: deps.sessionManager.getSession(
           id.split(':')[0],
-          id.split(':').slice(1).join(':')
+          id.split(':').slice(1).join(':'),
         ).getHistory().length,
       }));
       return makeResponse(request.id, { sessions });