Fix: passkey sound now layers in on password fields

RemSound's password boxes are deliberately NOT PasswordChar-masked (a screen-reader user can't see
a mask), so the key-click hook's "is this a password field?" check (UseSystemPasswordChar /
PasswordChar) was always false and the distinct passkey.wav never played. Password fields now mark
themselves with Tag = KeyClickService.PasswordFieldTag, and the hook checks that (keeping the
masking-flag check as a fallback). Tagged both password fields - ProfilePasswordDialog (which all
password entry routes through, including the send/receive streaming gate) and
ProfilePasswordManagerDialog. So a key click + passkey now layer together on every password keystroke.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.App/ProfilePasswordDialog.cs

@@ -38,6 +38,8 @@ internal static class ProfilePasswordDialog
             Dock = DockStyle.Top,
             Width = 400,
             AccessibleName = $"Password for profile {profileTitle}",
+            // Mark as a password field so the key-click hook layers in the passkey sound.
+            Tag = KeyClickService.PasswordFieldTag,
         };
         var hint = new Label
         {