Bash common.sh: consolidate docker_cmd/retry_docker/verify_running/emby_api, fix tailscale dups

common.sh gains:
- docker_cmd() + verify_running() + retry_docker() — removed from all 3 Docker_Essentials
  scripts where they were byte-for-byte duplicates
- emby_api(endpoint, [timeout=30]) — removed from 6 Media/Tools scripts that each defined
  their own _emby_api() with the same curl/parse/error pattern; call sites renamed emby_api
- format_duration() extended with days/hours branch (was capped at minutes+seconds)
- notify() comment: scripts do not need to preflight the notify script via validate_unraid_cmd

Tailscale deduplication:
- arr_sync.sh: _resolve_node_ip() and inline block in _delete_remote_item() both replaced
  with resolve_tailscale_ip() from common.sh
- git_pull_execute.sh: inline tailscale ip -4 replaced with resolve_tailscale_ip() (adds
  the tailscale status fallback that was missing)

Media/playback_aware_lidarr_discovery.sh

@@ -186,18 +186,6 @@ fi
 # ── API HELPERS ───────────────────────────────────────────────────────────────────────────────
 # ==============================================================================================
 
-_emby_api() {
-    local endpoint="$1"
-    local response http_code body
-    response=$(curl -sf --max-time 15 \
-        -H "X-Emby-Token: $EMBY_API_KEY" \
-        -w "\n%{http_code}" \
-        "${EMBY_URL}/${endpoint}" 2>/dev/null)
-    http_code=$(echo "$response" | tail -1)
-    body=$(echo "$response" | head -n -1)
-    [[ "$http_code" != "200" ]] && { error "Emby API HTTP $http_code: $endpoint"; return 1; }
-    echo "$body"
-}
 
 _lidarr_get() {
     curl -sf --max-time 20 \
@@ -329,7 +317,7 @@ CUTOFF_ISO=$(date -d "${LOOKBACK_DAYS} days ago" '+%Y-%m-%dT%H:%M:%SZ')
 TODAY_EPOCH=$(date +%s)
 TODAY=$(date +%Y-%m-%d)
 
-ACTIVITY_JSON=$(_emby_api "System/ActivityLog/Entries?MinDate=${CUTOFF_ISO}&Limit=5000") || {
+ACTIVITY_JSON=$(emby_api "System/ActivityLog/Entries?MinDate=${CUTOFF_ISO}&Limit=5000") || {
     error "Could not fetch Emby activity log"
     exit 1
 }
@@ -512,7 +500,7 @@ LIDARR_NAMES=$(echo "$LIDARR_ARTISTS_JSON" | jq -r '.[].artistName' 2>/dev/null)
 LIDARR_COUNT=$(echo "$LIDARR_NAMES" | grep -c . 2>/dev/null || echo 0)
 log "$LIDARR_COUNT artists in Lidarr"
 
-EMBY_LIBRARY_JSON=$(_emby_api "Items?IncludeItemTypes=MusicAlbum&Recursive=true&Fields=AlbumArtists&Limit=10000") || {
+EMBY_LIBRARY_JSON=$(emby_api "Items?IncludeItemTypes=MusicAlbum&Recursive=true&Fields=AlbumArtists&Limit=10000") || {
     warn "Could not fetch Emby artist library — skipping Emby filter"
     EMBY_ARTIST_NAMES=""
 }