feat: Tailscale resolution hardening, partnership offboard completion, Emby provisioning

common.sh:
- Add resolve_tailscale_ip() helper — tries `tailscale ip -4` first, falls back to
  parsing `tailscale status` output; handles hosts where MagicDNS short-name resolution
  is not active
- Add PARTNERSHIP_OWN_CONTAINERS alias in detect_hosts()
- Add aliasing for 4 Emby provisioning vars (PARTNERSHIP_PROVISION_EMBY_ADMIN,
  PARTNERSHIP_EMBY_ADMIN_USER, PARTNERSHIP_EMBY_ADMIN_PASS, PARTNERSHIP_EMBY_PORT)

Partnership/partnership_manager.sh:
- Replace 9 bare `tailscale ip -4` calls with resolve_tailscale_ip()
- Add read_remote_conf_var() and read_remote_conf_array() — SSH to mirror, source its
  own load_config.sh + detect_hosts(), return aliased variable; solves sparse-checkout
  problem where HOST1 cannot read master_host2.conf directly
- Add derive_short_name() — strips unraid- prefix, capitalises first char
- Add cleanup_partner_containers() — removes partner containers via FolderView3 folder
  if enabled, else falls back to FALLBACK_*_COVERS_*_TIER* arrays
- Add cleanup_owner_containers_on_mirror() — SSH to mirror, stops and removes containers
  matching *-${OWNER_SHORT} naming convention
- Add start_own_stack() and start_mirror_own_stack() — restart own containers locally
  or on mirror via SSH using PARTNERSHIP_OWN_CONTAINERS
- Add provision_emby_admin() — reads mirror credentials via read_remote_conf_var, checks
  for username collision, creates user + sets password + grants admin policy via Emby API
- Add revoke_emby_admin() — looks up mirror username on local Emby, deletes via REST API
- Wire offboard paths (both mirror-initiated and owner-initiated) to call container
  cleanup and stack restart; update --check finalisation paths accordingly
- Fix write_state_file in --onboard not gated on DRY_RUN (was writing ACTIVE state on
  dry runs)

master_host1.conf:
- Add HOST1_PARTNERSHIP_OWN_CONTAINERS array
- Add partnership Emby provisioning config (toggle + port + per-host credentials)

master_host2.conf:
- Add HOST2_PARTNERSHIP_OWN_CONTAINERS array
- Add HOST2_PARTNERSHIP_EMBY_ADMIN_USER and HOST2_PARTNERSHIP_EMBY_ADMIN_PASS

Tailscale fix applied to:
- Initial_run/ssh_setup.sh (2 callsites)
- unRAID_Essentials/rsync_stop.sh (1 callsite)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Orchestrators/critical_sync_maintenance.sh

@@ -197,10 +197,10 @@ if [[ "${PARTNERSHIP_ENABLED:-false}" == true ]]; then
     [[ "$DRY_RUN" == true ]] && PARTNER_DRY="--dry-run"
 
     if [[ "$RSYNC_OK" == true ]]; then
-        bash "$SCRIPT_DIR/partnership_manage.sh" \
+        bash "$SCRIPT_DIR/../Partnership/partnership_manager.sh" \
             --check --remote-seen $PARTNER_DRY
     else
-        bash "$SCRIPT_DIR/partnership_manage.sh" \
+        bash "$SCRIPT_DIR/../Partnership/partnership_manager.sh" \
             --check --remote-unseen $PARTNER_DRY
     fi
 else