feat: add health check

src/app.controller.ts

 import { Controller, Get } from '@nestjs/common';
-import { AppService } from './app.service';
 @Controller()
 export class AppController {
-  constructor(private readonly appService: AppService) {}
+  private start: number;
 
-  @Get()
-  getHello(): string {
-    return this.appService.getHello();
+  constructor() {
+    this.start = Date.now();
+  }
+
+  @Get('healthcheck')
+  async healthcheck() {
+    const now = Date.now();
+    return {
+      status: 'API Online',
+      uptime: Number((now - this.start) / 1000).toFixed(0),
+    };
   }
 }

src/app.module.ts

 import { Module } from '@nestjs/common';
 import { MongooseModule } from '@nestjs/mongoose';
 import { AppController } from './app.controller';
-import { AppService } from './app.service';
 import { StructuresModule } from './structures/structures.module';
 import { ConfigurationModule } from './configuration/configuration.module';
 import { CategoriesModule } from './categories/categories.module';
-
 @Module({
   imports: [
     ConfigurationModule,
@@ -16,6 +14,5 @@ import { CategoriesModule } from './categories/categories.module';
     CategoriesModule,
   ],
   controllers: [AppController],
-  providers: [AppService],
 })
 export class AppModule {}

src/app.service.ts

-import { Injectable } from '@nestjs/common';
-
-@Injectable()
-export class AppService {
-  getHello(): string {
-    return 'Hello World!';
-  }
-}