fix(ios): restrict authentication capabilities and validate bootstrap types

Require iOS 18.4 for explicit upload denial in the isolated authentication window. Add origin-bound generated download policy, app-switcher privacy, typed metadata regressions and original community icon assets. Seven portable tests and Swift formatting checks pass; Apple SDK validation remains external.

ios/project.yml

@@ -2,7 +2,7 @@ name: Yuvomi
 options:
   bundleIdPrefix: community.yuvomi
   deploymentTarget:
-    iOS: "16.0"
+    iOS: "18.4"
 settings:
   base:
     SWIFT_VERSION: "5.0"
@@ -40,6 +40,7 @@ targets:
       base:
         PRODUCT_BUNDLE_IDENTIFIER: community.yuvomi.mobile
         TARGETED_DEVICE_FAMILY: "1,2"
+        ASSETCATALOG_COMPILER_APPICON_NAME: AppIcon
     dependencies:
       - sdk: WebKit.framework
   YuvomiTests: