Prepare portable builds and validation diagnostics

[Has-X]

What changed

• Add Linux ARM64 and native desktop packages while keeping Ubuntu runners on 24.04.
• Align the portable GUI with the CLI ROM download flow and Sensitivity branding.
• Clarify platform-specific CLI executable names in the documentation.
• Fix flash: server returns "success" but validation did not return a token (v1.1.1) #8 response parsing for casing and wrapper variants.
• Add a redacted flash --dump-json <PATH> diagnostic that preserves response structure without exposing scalar values or lengths.

The PR stays in draft until the #8 reporter tests the Windows artifact on the affected yunluo recovery. A successful offline build does not prove a real recovery flash.

Local validation

• cargo fmt --all -- --check
• cargo test --workspace --locked (32 passed)
• cargo clippy --workspace --all-targets --locked -- -D warnings
• pwsh -NoProfile -File tools/check-locales.ps1
• cargo check --manifest-path fuzz/Cargo.toml --locked
• pwsh -NoProfile -File tools/preflight.ps1

Safety

No device captures, serial numbers, validation tokens, or private ROM URLs are included. Flash, wipe, and ADB policy behavior remains unchanged.