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/members/members.service.ts

@@ -1,7 +1,7 @@
 import { Injectable } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
-import { GuildMember } from '../entities/guild-member.entity';
+import { GuildMember } from '../entities/guild-member.entity.js';
 
 @Injectable()
 export class MembersService {