style(web): eigene Module ohne Kopfzeile, "In neuem Tab oeffnen" in der App-Leiste

Name- und Hinweiszeile ueber dem Rahmen entfallen (Name steht schon in der
App-Leiste, Nutzerwunsch 29.09.); der Link wandert per Portal in
HEADER_ACTIONS_SLOT_ID. Ungenutzter Schluessel customModules.embedHint weg.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

apps/web/src/messages/en.json

@@ -1364,7 +1364,6 @@
   },
   "customModules": {
     "openInNewTab": "Open in new tab",
-    "embedHint": "Some pages cannot be embedded. If this one stays blank, open it in a new tab.",
     "notFound": "This module no longer exists.",
     "invalidUrl": "This module's address is not a valid https address and is therefore not shown.",
     "loading": "Loading …",