Linux x86_64 offline release; configurable API and bundled PostgreSQL ports.

- packaging/linux: netx-<ver>-linux-x86_64.tar.gz with bundled Python 3.12,
  PostgreSQL 16 and web/dist (glibc >= 2.17). install.sh (install/update/
  reinstall), netxctl (start/stop/status/logs, set-port, set-bind,
  set-pg-port, reconfigure-db, check-update/update/auto-update, backup,
  uninstall), systemd units, nohup fallback without systemd. Privilege
  drop, detaching and tar go through the bundled Python, so bare images
  without su/runuser/setsid/tar work.
- Updates: same GitHub/Forgejo/manifest sources as Windows, sha256
  verified, pre-update pg_dump, automatic rollback when the new version
  does not come up.
- Non-loopback bind: generated bootstrap admin password and
  NETX_UME_VERIFY_TLS=true, as security_bootstrap requires.
- Build in manylinux2014 + check_bundle.sh (GLIBC <= 2.17, no missing
  libs); release-linux.yml builds on v* tags and smoke-tests offline on
  CentOS 7, Rocky 9, Ubuntu 18.04/24.04, Debian 12, openSUSE Leap 15 and
  openEuler 22.03 before attaching to the release.
- Windows: Setup DB page gets a bundled PG port field and
  /BundledPgPort=; set_pg_port.ps1 + tray "Built-in database port";
  reconfigure keeps the configured port; postgresql.conf is written
  without a BOM (PS 5.1 Set-Content -Encoding utf8 broke postgres).
- Forgejo/GitHub publish scripts include the Linux package.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packaging/build_release.ps1

@@ -121,7 +121,7 @@ foreach ($name in @(
         "download_postgres.ps1", "setup_first_run.ps1", "start_netx_app.ps1",
         "stop_netx_app.ps1", "update_netx.ps1", "check_update.ps1",
         "launch_shortcut.ps1", "netx_tray.ps1", "install_autostart.ps1", "install_service.ps1",
-        "service_run.ps1", "service_lifecycle.ps1", "install_update_task.ps1", "repair_venv.ps1", "runtime_ctl.ps1", "uninstall_prepare.ps1", "uninstall_delete_data.ps1", "sign_release.ps1",
+        "service_run.ps1", "service_lifecycle.ps1", "install_update_task.ps1", "repair_venv.ps1", "runtime_ctl.ps1", "set_pg_port.ps1", "uninstall_prepare.ps1", "uninstall_delete_data.ps1", "sign_release.ps1",
         "build_release.ps1", "publish_release.ps1", "publish_forgejo_release.ps1", "README.md", "manifest.example.json"
     )) {
     $src = Join-Path $PSScriptRoot $name