build(deps-dev): update scipy requirement from >=1.11 to >=1.18.1

Updates the requirements on [scipy](https://github.com/scipy/scipy) to permit the latest version.
- [Release notes](https://github.com/scipy/scipy/releases)
- [Commits](scipy/scipy@v1.11.0...v1.18.1)

---
updated-dependencies:
- dependency-name: scipy
  dependency-version: 1.18.1
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements-dev.txt

@@ -5,6 +5,6 @@
 # numpy-Floor 2.5.1: numpy 2.5.x traegt Requires-Python >=3.12 (keine cp310/cp311-
 # Wheels) -- moeglich, seit py3.10/3.11 fleet-weit gedroppt sind (Marco-Entscheid 2026-07-14).
 numpy>=2.5.2
-scipy>=1.11
+scipy>=1.18.1
 pytest>=9.1.1
 ruff>=0.16.5