General refresh

[ndevenish]

• Migrate CI to use branch "main" instead of "master"
• List test/doc dependencies in pyproject.toml
• Use UV pip compile to generate requirements.txt
• Update minimum python to 3.9 (dials will move to 310 soon)
• Remove CI syntax checking that is now done by pre-commit.ci

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 56.52%. Comparing base (c99a613) to head (3ab83e8).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #474   +/-   ##
=======================================
  Coverage   56.52%   56.52%           
=======================================
  Files           6        6           
  Lines         368      368           
=======================================
  Hits          208      208           
  Misses        160      160