Declare the drag-identifier UTType correctly across bundles

[bradleymackey]

Problem

UTType(exportedAs: "vault.identifier.drop.id") in VaultItem+Transferable.swift is evaluated in every bundle that links VaultiOS — including the autofill extension, whose code selector embeds VaultItemFeedView and therefore registers the .draggable/.dropDestination transfer types. exportedAs on an identifier the calling bundle does not declare is a programming error at runtime (fault log, undefined type resolution), and:

• VaultAppAutofill/Info.plist declared nothing at all;
• the main app's UTExportedTypeDeclarations entry was malformed — UTTypeConformsTo containing a single empty string and an empty UTTypeTagSpecification dict.

Fix

• Code: UTType(importedAs: "vault.identifier.drop.id", conformingTo: .data) — correct for shared code evaluated in multiple bundles; never faults on an undeclared identifier. The identifier itself is unchanged, so drag payloads are unaffected.
• Main app plist: repaired the export — conforms to public.data, added a description, dropped the empty tag-specification dict.
• Autofill extension plist: added the matching UTImportedTypeDeclarations entry.

Verification

• plutil -lint passes on both plists.
• Full VaultApp scheme (app + both extensions) builds for the simulator.
• App installed and launched on iPhone 18 Pro Max sim; feed renders (drag/drop types registered) with no UTType fault in the unified log.

⚠️ Automatic CI is still disabled (#548), so this is local verification only.

🤖 Generated with Claude Code