feat(mobile): adopt core 2.60.1 and stream native Cloud files

[adibhanna]

Summary

• Adopt clean core-2.60.1-core.h05ebb55c14afffb2 from merged source 4c74b478148a68adc8d77cc5c0d54a46ab469342.
• Add native verified file snapshots, signed uploads/downloads, confined vault paths, and correct incremental UTF-8 validation.
• Preserve iCloud placeholder semantics, local conflict bytes, safe rollback, keep-both retries, and account-bound cancellation.

Verification

• Package provenance, boundaries, typecheck, full Node suite, and production Swift helper regression tests passed.
• App and UI-test targets compile with the existing iOS 15 deployment floor.
• Clean artifact: real local Laravel/PostgreSQL/MinIO 200 MB Android-to-iOS transfer passed with matching source/storage/receiver SHA-256.
• Interrupted 50 MB native download discarded partial bytes and retried successfully.
• 52 repository/staging regressions pass, including publication failure, edited conflict copies, and failed rollback.
• Normal app assets restored after disposable qualification; the local-only control fixture is excluded from this PR.

Release

Backend dependency ZenNotes/website#55 is deployed; core source ZenNotes/zennotes#884 is merged. This prepares source integration, not an App Store submission. Physical-device/provider acceptance and publication of the core draft remain separate. No app version/build bump or public Cloud launch flags change.