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.swift

@@ -0,0 +1,22 @@
+// swift-tools-version: 5.9
+import PackageDescription
+
+let package = Package(
+    name: "FileOpener",
+    platforms: [.iOS(.v15)],
+    products: [
+        .library(name: "FileOpener", targets: ["FileOpenerPlugin"])
+    ],
+    dependencies: [
+        .package(url: "https://github.com/ionic-team/capacitor-swift-pm.git", from: "8.0.0")
+    ],
+    targets: [
+        .target(
+            name: "FileOpenerPlugin",
+            dependencies: [
+                .product(name: "Capacitor", package: "capacitor-swift-pm"),
+                .product(name: "Cordova", package: "capacitor-swift-pm")
+            ],
+            path: "ios/Sources/FileOpenerPlugin")
+    ]
+)