chore: justfile + license maintenance

[adamXbot]

Adds a root justfile per the org convention (recipes delegate to the existing CI/release commands) and unifies the MIT copyright holder to "Adam Kostarelas" (SPDX type unchanged).

just --list output:

Available recipes:
    default         # List available commands

    [dev]
    clean           # Remove build and release outputs
    setup           # Generate BananaBlitz.xcodeproj from project.yml (requires xcodegen)
    test            # Build and run the unit tests (unsigned Debug, same as CI)

    [ship]
    release version # Tag v<version> and push it to trigger the release workflow
    release-local   # Build, sign, notarize and package the DMG locally (needs Developer ID + notary env)

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