Fix Photos save for images + add native Quick Look file preview

Photos/Files bug: the lightbox download handed nativeSaveFile a bare
"/files/<id>" with no name, extension, or mime. Empty mime made
bzSaveToPhotos short-circuit as "notmedia" — so saveToAlbum (and its
permission prompt) never ran, and the image landed in the generic Files
folder as an extension-less blob. Now nativeSaveFile trusts the server's
Content-Type when the mime is unknown and appends a real extension
(bzExtForMime/bzEnsureExt), so images reach the Images folder AND Photos.

File preview: replace the @capacitor/share "share sheet" open with a new
native FileOpener plugin (QLPreviewController). bzOpenFile now prefers a
real Quick Look preview and only falls back to the share sheet if the
plugin isn't in the build. Wired file-opener into mobile/package.json and
the codemagic SPM diagnostics loop.

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

mobile/package.json

@@ -11,6 +11,7 @@
   },
   "dependencies": {
     "audio-route": "file:plugins/audio-route",
+    "file-opener": "file:plugins/file-opener",
     "media-library": "file:plugins/media-library",
     "native-call": "file:plugins/native-call",
     "share-inbox": "file:plugins/share-inbox",