Guard two constants the Windows target leaves unused

secrets.rs names the keyring service and desktop_client.rs the socket
timeout, and every use of both sits under a cfg that a Windows build
does not satisfy — the placeholder secret store has nothing to file
under, and the Nextcloud client's named pipe is not opened yet. The
first cross-compile reported both as dead code, which is a failed
clippy job the moment the Windows leg runs with -D warnings. Guarded
by the same cfgs as their users, with the reason beside each.

platform/dr-plat/src/secrets.rs

@@ -97,6 +97,10 @@ pub trait SecretStore: Send + Sync {
 }
 
 /// The service name entries are filed under.
+///
+/// Used by the two stores that have somewhere to file them; the placeholder
+/// below has nothing to name, and a Windows build otherwise warns here.
+#[cfg(any(all(unix, not(target_os = "android")), target_os = "android"))]
 const SERVICE: &str = "DarkRoom";
 
 /// Secret Service implementation (GNOME Keyring, KWallet via ksecretd).