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/arr_sync.sh

@@ -315,12 +315,8 @@ _delete_remote_item() {
     local node_id="$1" port="$2" api_ver="$3" endpoint="$4" config_xml="$5"
     local id_field="$6" id_type="$7" stable_id="$8"
     local node_name="${!node_id}"
-    local ts_name="${node_name,,}"
     local node_ip
-    node_ip=$(tailscale ip -4 "$ts_name" 2>/dev/null)
-    [[ -z "$node_ip" ]] && node_ip=$(tailscale status 2>/dev/null | \
-        awk -v n="$ts_name" '$2 ~ "^" n { print $1; exit }')
-    [[ -z "$node_ip" ]] && return 1
+    node_ip=$(resolve_tailscale_ip "$node_name") || return 1
 
     local select_expr
     if [[ "$id_type" == "string" ]]; then
@@ -478,14 +474,7 @@ fi
 
 _resolve_node_ip() {
     local node_id="$1"
-    local node_name="${!node_id}"
-    local ts_name="${node_name,,}"
-    local ip
-    ip=$(tailscale ip -4 "$ts_name" 2>/dev/null)
-    [[ -z "$ip" ]] && ip=$(tailscale status 2>/dev/null | \
-        awk -v n="$ts_name" '$2 ~ "^" n { print $1; exit }')
-    [[ -z "$ip" ]] && return 1
-    echo "$ip"
+    resolve_tailscale_ip "${!node_id}"
 }
 
 # Check if arr is reachable on remote node