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/plugins/file-opener/package.json

@@ -0,0 +1,27 @@
+{
+  "name": "file-opener",
+  "version": "1.0.0",
+  "description": "Preview a downloaded file with native iOS Quick Look for Biz Connect",
+  "main": "dist/plugin.cjs.js",
+  "module": "dist/esm/index.js",
+  "types": "dist/esm/index.d.ts",
+  "author": "BizGaze",
+  "license": "MIT",
+  "files": [
+    "dist/",
+    "ios/",
+    "FileOpener.podspec",
+    "Package.swift"
+  ],
+  "capacitor": {
+    "ios": {
+      "src": "ios"
+    }
+  },
+  "devDependencies": {
+    "@capacitor/core": "^8.0.0"
+  },
+  "peerDependencies": {
+    "@capacitor/core": "^8.0.0"
+  }
+}