Add Python 3.14 free-threading build support

[ericbuehl]

With the release of Python 3.14, the new free-threaded (no-GIL) mode is becoming more widely used.

It would be great if clickhouse-connect could provide prebuilt wheels and confirm compatibility with python3.14t (the free-threaded ABI).

[joe-clickhouse]

Hi @ericbuehl, thanks for bringing this up. In it's current form, clickhouse-connect doesn't stand to benefit greatly in terms of performance by going GIL-free. However, we are definitely aware that people are starting to build GIL-free applications that also depend on clickhouse-connect and need compatible wheels. I don't anticipate it taking TOO much work to get there so we'll seriously look at getting on our short-term roadmap!