fix(app): nothing secret is copied

The reading of the full reading's fixes found that copied recovery codes
and authenticator keys still reached clipboard histories (Windows, KDE's
Klipper, Gboard, Samsung's) and cloud clipboards, as no Flutter engine
marks a copy as sensitive, and that on Android an app in the background
can't empty the clipboard again, so the minute's clearing often never
happened.

As the developer decided: recovery codes are saved, like the phrase; an
authenticator's key is scanned as a QR code, opened in the authenticator
app, or typed from the screen. copySecret and its texts go.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyon_app/lib/l10n/halkyon_app_de.arb

@@ -80,8 +80,6 @@
   "passwordContinue": "Weiter",
   "passwordBack": "Zurück",
   "passwordDone": "Fertig",
-  "passwordCopy": "Kopieren",
-  "passwordCopied": "Kopiert.",
   "passwordSave": "Als Datei speichern",
   "passwordQrCode": "QR-Code für deine Authenticator-App",
   "passwordMailCode": "Code aus der E-Mail",