fix(debyltech-cloud): external signers, proxy trust, light-only mail

- Enable LibreSign's email identify method (click-to-sign, no account
  creation), remove the stamp background and collect signer metadata.
  On Skudak these were only ever set in the admin UI. Without the email
  method a fresh instance answers "No signers." for any outside address.
  The verify script now asserts it.
- Store add_footer=true explicitly. The code already defaults to it, but
  the 14.2 admin page shows unset as unchecked.
- trusted_proxies = the container's own address, read per deploy. Behind
  rootless port forwarding every request arrives from it, so without this
  X-Forwarded-For was ignored and every client shared one IP for
  brute-force throttling.
- maintenance_window_start and default_phone_region, which clears the setup
  warnings.
- Mail declares color-scheme "light only" so Apple Mail's dark mode doesn't
  repaint the white ground and bury the black wordmark (asserted in verify).
- Idempotency: redis image fully qualified (docker.io/library/...), the
  debyltechmail copy owned by the mapped www-data uid, and theming
  compared before setting.

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

ansible/roles/podman/files/debyltechmail/lib/Mail/DebyltechEMailTemplate.php

@@ -188,6 +188,21 @@ class DebyltechEMailTemplate extends EMailTemplate {
 			'font-size:26px;font-weight:300;letter-spacing:-0.02em',
 			$this->heading,
 		);
+
+		// Opt out of mail-client dark mode. Without this Apple Mail repaints
+		// the white ground charcoal on its own, and the black wordmark all but
+		// disappears. Swapping to a white logo under prefers-color-scheme is
+		// NOT a fix: with Apple Mail's "Use dark backgrounds for messages" off,
+		// the query still matches while the ground stays white, leaving a
+		// white-on-white logo. This mail is designed light; render it light.
+		$this->head = str_replace(
+			'</head>',
+			'<meta name="color-scheme" content="light only">'
+				. '<meta name="supported-color-schemes" content="light only">'
+				. '<style type="text/css">:root{color-scheme:light only;supported-color-schemes:light only}</style>'
+				. '</head>',
+			$this->head,
+		);
 	}
 
 	/**