Bundled builds: ship Qt WebEngine (helper process, resources)

When a bundled library is Qt WebEngine, the bundler also installs
QtWebEngineProcess (plus its libraries) to libexec/, the resources and
the en-US/de locales, and points qt.conf at them. The cross image unpacks
the arm64 QtWebEngineProcess (its package can't be co-installed with the
amd64 one). Experiment for DSH-1: the Frame's system WebEngine (6.7.0,
built against FFmpeg 6) can't be loaded.

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

CMakePresets.json

@@ -41,7 +41,8 @@
       "cacheVariables": {
         "CMAKE_BUILD_TYPE": "RelWithDebInfo",
         "VRDASH_DEPLOY_QT": "ON",
-        "VRDASH_BUILD_TESTS": "OFF"
+        "VRDASH_BUILD_TESTS": "OFF",
+        "VRDASH_WEBENGINE_PROCESS": "/opt/qt6-arm64/usr/lib/qt6/libexec/QtWebEngineProcess"
       }
     },
     {