Fix dead/incorrect vars and consolidate duplicated logic into common.sh

Codebase-wide audit pass: fixed real bugs (SSH hangs missing BatchMode,
local-outside-function no-ops, variable name collisions, a truncated
ratio calc, wrong state-dir path, DARK vs NO_INTERNET drift, and more),
then pulled logic that was duplicated across multiple scripts — arr
cleanup safety gates, docker restart ordering, container maintenance
stop/restart, watchdog state-file helpers, partnership role resolution,
cert expiry checks, remote node discovery, and TMDB discovery scoring —
into common.sh so each now has a single implementation.

Monitors/emby_session_report.sh

@@ -316,7 +316,7 @@ echo ""
 echo "━━━ $ICON_RAM Transcode Status ━━━"
 if mountpoint -q "$RAMDISK_PATH" 2>/dev/null; then
     RAMDISK_USED_KB=$(df "$RAMDISK_PATH" --output=used 2>/dev/null | tail -1 | tr -d ' ')
-    RAMDISK_USED_GB=$(awk "BEGIN {printf \"%.2f\", ${RAMDISK_USED_KB:-0} / 1048576}")
+    RAMDISK_USED_GB=$(kb_to_gb "$RAMDISK_USED_KB")
     SYMLINK=$(readlink "$TRANSCODE_LINK" 2>/dev/null || echo "unknown")
     echo "  $ICON_RAM  Ramdisk usage:  ${RAMDISK_USED_GB}GB / ${RAMDISK_SIZE:-8G}"
     echo "  $ICON_LINK Symlink target: $SYMLINK"