Improve Makefile & fix interpreter version

[Manu-sh]

Hi, i tryied to install for my distribution via pip (pipx on Archlinux) but for some reason the version installed doesn't have the latest changes so dns-benchmark benchmark --resolvers='Cloudflare,Google,Quad9' --domains='ping-eu.ds.on.epicgames.com' say that there is no file.

so i cloned the repo and notice 2 possible improvements:

1. i typed make, thats throw me an error bc. i should use pipx instead of pip on my distro or i should create a virtual env, thus i defined the $(PIP) variable make easier to replace in future if needed (however tests doesn't work well without using a virtualenv because of the following command python -m dns_benchmark.cli --help in test_cli_command[cmd_19] but the command seems fine).

2. the interpreter requirement version in pyproject.toml are >=3.9,<3.13 and refuse to build, but i changed the upper bound to 3.14.3 (which is my current version) and seems that works fine too. However i only tested my use-case and i don't know if is possible change the python version without breaking the code, but all tests passes.

Probably an upper bound on python version isn't required at all at least for now (?)

Tests

i runned tests with make test everything seems fine with python 3.14.3

python -m venv venv
source venv/bin/activate
make install-dev
make install-pdf
make test