…gnature (oapi-codegen#1419)

* hotfix:
- Bump fiber version to 2.52.0
- Adopted middleware template for fiber to handle new GetReqHeader() method, that has changed signature in fiber 2.50.0 (https://github.com/gofiber/fiber/releases/tag/v2.50.0)

* Use latest fiber, and fix go deps

The latest Fiber requires Go 1.24, therefore, we have to increase
the version in the modules which use it. This is constrained to
tests and examples, so it doesn't affect the main repo.

Go 1.24 can't compile the version of golang.org/x/tools which we
were using, so update that as well.

* fix: use valueList[0] for fiber header IsPassThrough case

The merge with upstream/main resolved a conflict in the fiber
middleware template's header IsPassThrough handler by taking
upstream's version, which still used the old single-string `value`
variable. This is incorrect because fiber 2.50.0+ changed
GetReqHeaders() to return map[string][]string. Fix by using
valueList[0] to match the rest of the header handling block.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Tidy up modules

This seems to be about the minimal set of changes to have
everything build and test cleanly.

* fix: add Go 1.24 version guards to Makefiles

The internal/test and examples modules now require Go 1.24+ in their
go.mod files, but their Makefiles lacked version guards, causing CI
failures on Go 1.22 and 1.23. Add execute-if-go-124 guards matching
the pattern used by other Go 1.24+ modules. Also bump the
strict-server/stdhttp Makefile guard from 1.22 to 1.24.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Alexey Boltunov <apboltunov@mts.ru>
Co-authored-by: Marcin Romaszewicz <marcinr@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>