* fix(xray): verify the release archive checksum before installing
UpdateXray downloaded the Xray-core release zip and installed the binary
from it after only a TLS fetch, an HTTP-200 check and a size cap — the
archive itself was never verified, so a corrupted or tampered release
asset would be extracted and run as the panel's xray binary.
Verify the downloaded archive against the SHA2-256 published in the
release's .dgst sidecar (which XTLS ships next to every asset) before
installing, and abort the update on mismatch, a missing/short SHA2-256
entry, or an unreachable .dgst. The digest parser and fetch are covered by
tests, including the real .dgst line format ("SHA2-256= <hex>").
* address review: clearer warning + re-download guidance on checksum mismatch
Per review feedback on the PR: on a SHA-256 mismatch, surface a plain-language
warning that the downloaded archive is corrupted or differs from the official
release and that the user should exit and re-download, instead of a terse
"checksum mismatch" error. The install still aborts so a mismatched binary is
never run; the message now tells the user the safe next step.
n0ctal
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