Add bot blocker functionality and update security middleware

- Introduced a bot blocker initialized with a user agent blocklist.
- Updated the security middleware to utilize the new bot blocker in both main and test files.
- Enhanced error handling for API requests to return a proper 404 response when content is not found.

main_test.go

@@ -46,11 +46,12 @@ func TestMainHandlers(t *testing.T) {
 
 	giteaServer = mockGitea.URL
 	statsService := stats.NewService("test-hashes.json")
+	botBlocker := security.NewBotBlocker("")
 	initialSoftware := config.LoadSoftware(configPath, giteaServer, "")
 	apiServer := api.NewServer("", initialSoftware, statsService)
 
 	r := chi.NewRouter()
-	r.Use(security.SecurityMiddleware(statsService))
+	r.Use(security.SecurityMiddleware(statsService, botBlocker))
 	r.Get("/api/software", apiServer.APISoftwareHandler)
 	r.Get("/api/stats", statsService.APIStatsHandler)
 	r.Get("/api/download", apiServer.DownloadProxyHandler)