Harden supply-chain CI, enforce strict media routing & add WUA support

[ClausValcaTD]

• Added OpenROM-bins checksum verification step in Release.yml, Flatpak.yml, build_linux.sh, build_mac.sh, and build_windows.bat.
• Enforced strict platform-to-media routing in core Converter._toChd() for unrecognized platforms when --media flag is omitted.
• Integrated NKit v3.1.0 Wii U .wua format detection, conversion matrix in README.md, and core tests.
• Updated settings UI label for Max Compression (Vorbis) in Flutter desktop GUI.

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PR created automatically by Jules for task 13204856439772484260 started by @ClausValcaTD

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