refactor: migrate to ES modules

package.json type=module, tsconfig module/moduleResolution=NodeNext,
target es2022, explicit .js on all relative imports. Center: jsonwebtoken
& bcryptjs switched to default imports (ESM/CJS interop). Verified:
builds, boots, full auth + plugin round-trip work under ESM.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/channels/turn-shuffle.ts

@@ -1,4 +1,4 @@
-import { RoundEvent } from '../entities/channel-turn-state.entity';
+import { RoundEvent } from '../entities/channel-turn-state.entity.js';
 
 export type ShuffleResult = { paused: true } | { paused: false; newOrder: string[] };