Improved static typing in dash.callback

[odorikakeru]

This PR improves static typing for the callback decorator by preserving wrapped function signatures in the callback decorator type contract.

Based on this conversation thread: [Feature Request] A "@dash.typed_callback" that plays more nicely with MyPy than "@dash.callback" #3691 - The decision was made to not implement @dash.typed_callback and instead update @dash.callback based on feedback.

Compliance tests added (not included in integration test directory as type hints don't affect run time behaviour).

DISCLOSURE: Testing code was written/edited with AI assistance.

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • Update callback decorator type signature
  • Add and validate callback decorator typing/runtime tests (some testing code written with AI assistance)
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
• If this PR needs a follow-up in dash docs, community thread, I have mentioned the relevant URLS as follows
  • this GitHub #PR number updates the dash docs
  • here is the show and tell thread in Plotly Dash community