feat(autostart): "Start with Windows" toggle

- PM.AutoStart wraps HKCU\Software\Microsoft\Windows\CurrentVersion\Run.
  Value "PMServer" = "<exe>" -tray. Per-user, no admin required, shows
  up in Task Manager → Startup so the user can override from there.

- UMainForm honours the -tray CLI flag (set by the registry entry):
  after the server starts, MinimizeToTray via TThread.ForceQueue so the
  app comes up directly in the tray with no visible window flash.

- Bridge cmd://autostart/{get,set} + Bridge.getAutoStart() /
  setAutoStart() / onAutoStartStatus(). Settings exposes a toggle in
  the Security section, visible only when Bridge.active (the PHP
  frontend can't touch the registry).

- Toggle reads "on" only when the registered command matches the
  current exe path, so a stale entry from a moved exe lets the user
  re-enable to refresh.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

delphi-backend/PMServer.dpr

@@ -18,6 +18,7 @@ uses
   PM.Bridge in 'Source\PM.Bridge.pas',
   PM.QuickUnlock in 'Source\PM.QuickUnlock.pas',
   PM.UserPrefs in 'Source\PM.UserPrefs.pas',
+  PM.AutoStart in 'Source\PM.AutoStart.pas',
   PM.ProcessLockdown in 'Source\PM.ProcessLockdown.pas',
   PM.Handler.Ping in 'Handlers\PM.Handler.Ping.pas',
   PM.Handler.Auth in 'Handlers\PM.Handler.Auth.pas',