fix(native-file): prevent crash when unlinking missing files
NativeFileSpec.unlink is codegened as a void-returning TurboModule
method, which dispatches asynchronously on the mqt_v_native thread.
Throwing "File does not exist" there bypasses every JS try/catch and
surfaces as a fatal AndroidRuntime exception, killing the process.
Make unlink idempotent (POSIX rm -f semantics): no-op when the path
does not exist. The Downloads "delete all" and individual delete
flows previously crashed whenever a chapter row had isDownloaded=true
while its on-disk folder had already been removed (e.g. after backup
restore or external cleanup). The same fix also protects useNovel,
pluginManager, fetch, epub/import, backup/local, backup/utils, and
AdvancedTab call sites that share the same native handler.
Jeon JaeHyeong
34be7a1234