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.

Transcodes/transcode_manager.sh

@@ -234,18 +234,15 @@ fix_permissions() {
 }
 
 get_ramdisk_used_gb() {
-    df "$RAMDISK_PATH" --output=used 2>/dev/null | \
-        tail -1 | tr -d ' ' | awk '{printf "%.2f", $1/1048576}'
+    kb_to_gb "$(df "$RAMDISK_PATH" --output=used 2>/dev/null | tail -1 | tr -d ' ')"
 }
 
 get_ramdisk_avail_gb() {
-    df "$RAMDISK_PATH" --output=avail 2>/dev/null | \
-        tail -1 | tr -d ' ' | awk '{printf "%.2f", $1/1048576}'
+    kb_to_gb "$(df "$RAMDISK_PATH" --output=avail 2>/dev/null | tail -1 | tr -d ' ')"
 }
 
 get_ssd_free_gb() {
-    df "$TRANSCODE_SSD" --output=avail 2>/dev/null | \
-        tail -1 | tr -d ' ' | awk '{printf "%.2f", $1/1048576}'
+    kb_to_gb "$(df "$TRANSCODE_SSD" --output=avail 2>/dev/null | tail -1 | tr -d ' ')"
 }
 
 get_flip_count() {