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.

.swift-format

@@ -0,0 +1,6 @@
+{
+  "version": 1,
+  "indentation": { "spaces": 4 },
+  "lineLength": 120,
+  "respectsExistingLineBreaks": true
+}