chore: inline build scripts into Justfile

[dylanmtaylor]

Migrates bazzite's local build system towards the pattern used by aurora/bluefin.

Changes:

• Inlines 8 shell scripts into Justfile recipes
• Adds _resolve_image and _container_mgr as reusable just helpers
• Resolves kernel version dynamically via skopeo inspect instead of relying on Containerfile defaults
• Passes all build args explicitly to podman build
• Updates ISO scripts to use just helpers instead of sourcing shell scripts

[codacy-production]

Not up to standards ⛔

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[dylanmtaylor]

just --list --unsorted:

Available recipes:
    [Just]
    just-check                           # Check Just Syntax

    [Image]
    build target="" image=""             # Build image
    run-container target="" image=""     # Run Container [alias: run]

    [ISO]
    build-iso-release target="" image="" # Build ISO [alias: build-iso]
    build-iso-git target="" image=""     # Build ISO using ISO Builder Git Head
    run-iso target="" image=""           # Run ISO

    [Utility]
    list-images                          # List Images
    clean-images                         # Clean Images
    clean-isos                           # Clean ISOs