chore: add community health files, templates, CI, and branding

[AhmedAredah]

Summary

• Add community health files, CODEOWNERS, funding placeholder, and issue/PR templates.
• Add Linux CI for Qt 6, CMake, private Container checkout via CONTAINER_REPO_TOKEN, Debug/Release builds, and ctest.
• Update README TerminalSim owner links and badges for AhmedAredah/TerminalSim.

Test plan

• git diff --check HEAD~1..HEAD
• Parsed GitHub YAML files with Ruby YAML.load_file
• Verified README no longer references VTTI-CSM/TerminalSim
• Verified git log --oneline origin/main..HEAD contains only this branding commit
• Local cmake configure succeeded; local build could not complete because /usr/local has Container 0.1.0, while TerminalSim requires newer Container APIs. CI builds Container v0.2.0 from the private repo.