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/common/center-api-key.guard.ts

@@ -1,8 +1,8 @@
 import { CanActivate, ExecutionContext, Injectable, UnauthorizedException } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
-import * as bcrypt from 'bcryptjs';
-import { GuildNode } from '../entities/guild-node.entity';
+import bcrypt from 'bcryptjs';
+import { GuildNode } from '../entities/guild-node.entity.js';
 
 @Injectable()
 export class CenterApiKeyGuard implements CanActivate {

src/common/metrics.controller.ts

@@ -1,5 +1,5 @@
 import { Controller, Get } from '@nestjs/common';
-import { MetricsService } from './metrics.service';
+import { MetricsService } from './metrics.service.js';
 
 @Controller('metrics')
 export class MetricsController {

src/common/request-context.middleware.ts

@@ -1,6 +1,6 @@
 import { randomUUID } from 'crypto';
 import { NextFunction, Request, Response } from 'express';
-import { MetricsService } from './metrics.service';
+import { MetricsService } from './metrics.service.js';
 
 type ReqWithId = Request & { requestId?: string };