* fix(test): enable Subsonic response snapshot tests on Windows
Replaced cupaloy with a simple custom snapshot matcher that normalizes
CRLF line endings before comparison. The tests were skipped on Windows
via a //go:build unix tag because Git for Windows checks out snapshot
files with CRLF, while Go's xml/json.MarshalIndent always produces LF,
causing direct string comparison to fail. The new matcher reads snapshot
files with os.ReadFile and normalizes \r\n to \n before comparing.
Also added a .gitattributes in the .snapshots directory to enforce LF
checkout, and removed the now-unused cupaloy dependency.
* fix(test): add UPDATE_SNAPSHOTS support to custom snapshot matcher
Restore the ability to update snapshots via `make snapshots`
(UPDATE_SNAPSHOTS=true), which was lost when replacing cupaloy
with the custom matcher.
