feat: Require iOS 27 across iOS targets

[kyleve]

Summary

• Require iOS 27.0 across the iOS apps, extensions, package products, and test bundles. The macOS minimum stays at 26.0.
• Remove the iOS 26.1 tab-accessory availability branch and inline the accessory in MainTabs.
• Update requirements and snapshot guidance. Native-glass settle floors remain because the iOS 27 snapshot suite still depends on them.

Why

The supported iOS runtime is now 27.0. The old deployment minimum kept an unreachable iOS 26.0 presentation path and prevented the follow-on SwiftData HistoryObserver migration.

Compatibility

Devices on iOS 26 cannot install this app version. Persistence, CloudKit schema, and backup formats do not change. Package.swift uses .iOS("27.0") because the manifest's Swift tools version 6.2 does not provide the .v27 shorthand.

Review focus

• The native tab accessory renders through the same existing status view on iOS 27.
• Snapshot settling and the iOS 27 tile-and-stitch workaround remain in place.

Testing

• ./ide --no-open — passed.
• ./swiftformat --lint — passed.
• BUMPER_EVALUATION_TIMEOUT_SECONDS=300 ./test --architecture-only — passed; the default 60-second budget timed out on the initial run.
• ./test --everything --skip-architecture — 2,023 iOS unit tests and 50 snapshot suites passed.
• mise exec -- tuist test Ledger-macOS-Tests --no-selective-testing -- -destination 'platform=macOS' — passed.

Stack

Base PR. PR #319 migrates WhereCore to HistoryObserver on top of this minimum-version change.