feat: add logging and caching enhancements across core services

Integrate `Logger` for consistent logging in services like `reports`, `categories`, `users`, `contents`, and more. Introduce caching capabilities with `CacheInterceptor` and manual cache clearing logic for categories, users, and contents. Add request throttling to critical auth endpoints for enhanced rate limiting.

backend/src/auth/auth.controller.ts

@@ -1,5 +1,6 @@
 import { Body, Controller, Headers, Post, Req, Res } from "@nestjs/common";
 import { ConfigService } from "@nestjs/config";
+import { Throttle } from "@nestjs/throttler";
 import type { Request, Response } from "express";
 import { getIronSession } from "iron-session";
 import { AuthService } from "./auth.service";
@@ -16,11 +17,13 @@ export class AuthController {
 	) {}
 
 	@Post("register")
+	@Throttle({ default: { limit: 5, ttl: 60000 } })
 	register(@Body() registerDto: RegisterDto) {
 		return this.authService.register(registerDto);
 	}
 
 	@Post("login")
+	@Throttle({ default: { limit: 5, ttl: 60000 } })
 	async login(
 		@Body() loginDto: LoginDto,
 		@Headers("user-agent") userAgent: string,
@@ -52,6 +55,7 @@ export class AuthController {
 	}
 
 	@Post("verify-2fa")
+	@Throttle({ default: { limit: 5, ttl: 60000 } })
 	async verifyTwoFactor(
 		@Body() verify2faDto: Verify2faDto,
 		@Headers("user-agent") userAgent: string,