Minor adaptions to run with root 6.38

[GernotMaier]

Mostly related to https://root.cern/doc/v638/release-notes.html#optimization-of-root-header-files

[Copilot]

Pull request overview

This PR adapts the codebase to work with ROOT 6.38, addressing header file optimization changes introduced in that version. The changes include adding missing header includes that were previously transitively included, fixing a type mismatch in a function signature, updating the Docker infrastructure to use Ubuntu-based images, and updating CI workflows to match.

• Adds explicit includes for <cmath> and TMath.h headers that are no longer transitively included in ROOT 6.38
• Fixes a type mismatch in VPlotAnasumHistograms::drawPSF() where a string parameter incorrectly had an integer default value
• Updates Docker images from AlmaLinux to Ubuntu and ROOT version from 6.30.02 to 6.32.04

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
inc/VPointingCorrectionsTreeReader.h	Adds <cmath> include for atan2() function
inc/VPlotAnasumHistograms.h	Fixes default parameter from integer 0 to empty string "" for string parameter
inc/VPedestalLowGain.h	Adds TMath.h include for ROOT math functions
inc/VGlobalRunParameter.h	Adds TMath.h include for ROOT math functions
docs/changes/323.maintenance.md	Documents the ROOT 6.38 compatibility changes
dockerfiles/Dockerfile	Updates base image from Alma9 to Ubuntu 24.04, ROOT version to 6.32.04, switches package manager from dnf to apt, improves shell quoting, and explicitly initializes LD_LIBRARY_PATH
.github/workflows/vts-eventdisplay-package.yml	Adds YAML front matter (---) for proper YAML document formatting
.github/workflows/ci-buildmatrix-cpp17.yml	Updates ROOT versions in test matrix, removes conditional logic for package installation (now all Ubuntu), switches to libopenblas-dev

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.