Polish before first GitHub push: consistent adapter usage and naming

stability_watchdog.sh mover check now uses platform_is_mover_running()
instead of raw pgrep, matching server_reboot.sh.

check_unraid_version_parity() renamed to check_os_version_parity() —
the function internals were already platform-neutral after the adapter
refactor; the name was the last Unraid artifact.

Monitors/backup_verify.sh

@@ -180,7 +180,7 @@ check_connectivity
 log "Connectivity to $REMOTE_SERVER_NAME ✅"
 
 # Version parity — mismatched unRAID could cause md5sum path differences
-check_unraid_version_parity || {
+check_os_version_parity || {
     warn "Version parity check failed — proceeding with caution"
     warn "Checksum results may be unreliable if md5sum path changed between versions"
 }