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)

Tools/emby_to_lidarr_sync.sh

@@ -89,18 +89,6 @@ fi
 # ── API HELPERS ───────────────────────────────────────────────────────────────────────────────
 # ==============================================================================================
 
-_emby_api() {
-    local endpoint="$1"
-    local response http_code body
-    response=$(curl -sf --max-time 30 \
-        -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 30 \
@@ -163,7 +151,7 @@ echo "━━━ $ICON_SYNC Emby Music Library ━━━"
 
 # Query MusicAlbum items and extract AlbumArtists — gives primary album artists only,
 # not the full tag credits (guest features, songwriters, etc.) that MusicArtist returns
-EMBY_ALBUMS_JSON=$(_emby_api "Items?IncludeItemTypes=MusicAlbum&Recursive=true&Fields=AlbumArtists&Limit=10000") || {
+EMBY_ALBUMS_JSON=$(emby_api "Items?IncludeItemTypes=MusicAlbum&Recursive=true&Fields=AlbumArtists&Limit=10000") || {
     error "Could not fetch Emby music albums"
     exit 1
 }