Refactor NameServer and other improvements

[nhairs]

Fixes: #6

Changes

• Drop Python 3.7 support.
• Add Python 3.10 support.
• Move tooling to uv.
• Add GitHub Actions test suite.
• Refactor NameServer and Middleware
• Add new CLI for running servers
• Add contributing.md and security.md
• Various updates to docs
• Transport fixes (cherry-picked from 4a0c23c)

Test Plan

• unit tests
• check docs using ./dev.sh docs

[nhairs]

Have uploaded rendered docs as dev: https://nhairs.github.io/nserver/dev/

[nhairs]

Hi @adulau, I can see you lurking in the reactions 😉 . I was wondering if you'd be willing to take a look at this PR at a high level (perhaps even just looking at the new docs) and letting me know if the new design makes sense as a potential consumer of the library? 🙏

(No pressure though)