fix(util): preserve LRU cache decorator types

[paulkagiri]

Summary of Changes

Use ParamSpec to type Falcon's internal LRU cache decorator factory so wrapped callables keep their original signatures and expose cache_clear() to static type checkers.

This removes the now-unnecessary type: ignore comments around cached resolver/status helpers and adds the narrow assertions needed where the ASGI testing client converts a collected response status after the app has responded.

Related Issues

Closes #2629

Pull Request Checklist

• Applied changes to both WSGI and ASGI code paths and interfaces (where applicable).
• Added tests for changed code.
• Performed automated tests and code quality checks by running tox.
• Prefixed code comments with GitHub nick and an appropriate prefix.
• Coding style is consistent with the rest of the framework.
• Updated documentation for changed code.
  • Added docstrings for any new classes, functions, or modules.
  • Updated docstrings for any modifications to existing code.
  • Updated both WSGI and ASGI docs (where applicable).
  • Added references to new classes, functions, or modules to the relevant RST file under docs/.
  • Updated all relevant supporting documentation files under docs/.
  • A copyright notice is included at the top of any new modules (using your own name or the name of your organization).
  • Changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives.
• Changes (and possible deprecations) have towncrier news fragments under docs/_newsfragments/, with the file name format {issue_number}.{fragment_type}.rst. (Run tox -e towncrier, and inspect docs/_build/html/changes/ in the browser to ensure it renders correctly.)
• LLM output, if any, has been carefully reviewed and tested by a human developer. (See also: Use of LLMs ("AI").)

Validation performed:

• python -m mypy --strict falcon
• python -m ruff format --check falcon/util/misc.py falcon/media/handlers.py falcon/http_error.py falcon/http_status.py falcon/response.py falcon/testing/client.py
• python -m ruff check falcon/util/misc.py falcon/media/handlers.py falcon/http_error.py falcon/http_status.py falcon/response.py falcon/testing/client.py
• python -m pytest tests/test_media_handlers.py tests/test_httpstatus.py tests/test_utils.py::TestFalconUtils::test_code_to_http_status tests/test_utils.py::TestFalconUtils::test_http_status_to_code tests/asgi/test_hello_asgi.py -q
• python tools/towncrier_draft.py --dry-run
• git diff --check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b1b683a) to head (710250d).

Additional details and impacted files

@@            Coverage Diff            @@
##            master     #2643   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           64        64           
  Lines         7976      7981    +5     
  Branches      1102      1102           
=========================================
+ Hits          7976      7981    +5     

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