refactor(handlers): standardize logging using request attributes helper

- Replace manual IP logging with the `withRequestLogAttrs` helper in authentication handlers.
- Add user activity logging for API documentation and login page views.
- Clean up log calls to use variadic expansion of request attributes.

backend/libs/httpserver/server.go

@@ -50,7 +50,6 @@ func New(cfg config.Config, logger *slog.Logger) (*http.Server, error) {
 		middleware.SecurityHeaders,
 		middleware.Gzip,
 		middleware.ClientIP(cfg.TrustedProxies),
-		middleware.Logger(logger),
 		middleware.Bans(logger, banService, cfg.TrustedProxies),
 	)