Evaluate migration to devcontainers Ubuntu 24.04 base image

[NGirchev]

Goal

Evaluate and, if safe, migrate the development container base image to:

FROM mcr.microsoft.com/devcontainers/base:ubuntu-24.04

Plan

1. Locate the current devcontainer/Dockerfile image definitions used by the repository.
2. Compare the current base image with mcr.microsoft.com/devcontainers/base:ubuntu-24.04:
   • OS packages and package manager behavior
   • Java 21 availability and installation path
   • Maven wrapper execution
   • Docker CLI / Compose availability if used inside the container
   • Node/npm availability for UI-related tooling if applicable
   • Locale, timezone, shell, git, and common CLI tools
3. Build the devcontainer image locally with the new base image.
4. Run required verification inside the rebuilt container:
   • ./mvnw clean compile
   • targeted tests for modules affected by environment/toolchain assumptions
   • Docker-related commands only if the devcontainer is expected to support them
5. Check startup and developer workflow:
   • IDE opens the project correctly
   • Maven caches and permissions work
   • generated files are owned by the workspace user, not root
6. Document any required package additions or config changes.
7. If verification passes, apply the base image change in a dedicated PR/commit.

Acceptance Criteria

• Devcontainer builds successfully on Ubuntu 24.04 base.
• Java 21 and Maven wrapper work without manual fixes.
• ./mvnw clean compile passes inside the container.
• Any required package/config deltas are documented.
• If migration is unsafe, blockers and rollback recommendation are documented.