feat(middleware): add crawler detection middleware for suspicious requests

Introduce `CrawlerDetectionMiddleware` to identify and log potential crawlers or bots accessing suspicious paths or using bot-like user agents. Middleware applied globally to all routes in `AppModule`.

backend/src/common/middlewares/crawler-detection.middleware.ts

@@ -0,0 +1,67 @@
+import { Injectable, Logger, NestMiddleware } from "@nestjs/common";
+import type { NextFunction, Request, Response } from "express";
+
+@Injectable()
+export class CrawlerDetectionMiddleware implements NestMiddleware {
+	private readonly logger = new Logger("CrawlerDetection");
+
+	private readonly SUSPICIOUS_PATTERNS = [
+		/\.env/,
+		/wp-admin/,
+		/wp-login/,
+		/\.git/,
+		/\.php$/,
+		/xmlrpc/,
+		/config/,
+		/setup/,
+		/wp-config/,
+		/_next/,
+		/install/,
+		/admin/,
+		/phpmyadmin/,
+		/sql/,
+		/backup/,
+		/db\./,
+		/backup\./,
+		/cgi-bin/,
+		/\.well-known\/security\.txt/, // Bien que légitime, souvent scanné
+	];
+
+	private readonly BOT_USER_AGENTS = [
+		/bot/i,
+		/crawler/i,
+		/spider/i,
+		/python/i,
+		/curl/i,
+		/wget/i,
+		/nmap/i,
+		/nikto/i,
+		/zgrab/i,
+		/masscan/i,
+	];
+
+	use(req: Request, res: Response, next: NextFunction) {
+		const { method, url, ip } = req;
+		const userAgent = req.get("user-agent") || "unknown";
+
+		res.on("finish", () => {
+			if (res.statusCode === 404) {
+				const isSuspiciousPath = this.SUSPICIOUS_PATTERNS.some((pattern) =>
+					pattern.test(url),
+				);
+				const isBotUserAgent = this.BOT_USER_AGENTS.some((pattern) =>
+					pattern.test(userAgent),
+				);
+
+				if (isSuspiciousPath || isBotUserAgent) {
+					this.logger.warn(
+						`Potential crawler detected: [${ip}] ${method} ${url} - User-Agent: ${userAgent}`,
+					);
+					// Ici, on pourrait ajouter une logique pour bannir l'IP temporairement via Redis
+				}
+			}
+		});
+
+		next();
+	}
+}