modernising dynamite

[IainHammond]

• setup.py was broken so I've created a pyproject.toml
• removed requirements.txt
• added .gitignore
• added casa_cube and celerite2 as dependencies
• removed alive_progress in favour of tqdm since most people will have that installed already
• fixed all of the syntax errors related to print statements
• upgrade celerite to celerite2

[gemini-code-assist]

Code Review

This pull request transitions the project to a modern PEP 517 build system using pyproject.toml, replaces alive-progress with tqdm, and migrates Gaussian Process functionality to celerite2. The reviewer identified several off-by-one errors in channel processing loops, a logic error where a kernel component was unintentionally overwritten, and an incorrect API call to celerite2 that would cause a runtime error. Additionally, feedback was provided to remove a premature Python 3.14 classifier and to use more idiomatic f-strings for plot titles.

[IainHammond]

none of the remaining Gemini suggestions are needed