Build first-value onboarding for Cubby 1.1.0

[barronlroth]

Summary

• Replace the single-field first run with a focused Welcome -> Home -> First Item -> Location -> Review flow.
• Atomically create the first home, Unsorted location, chosen location, and item only after review, with rollback on failure.
• Preserve existing-home recovery and present the hard subscription paywall only after the first real item is safely stored.
• Add Cubby versioning rules and set this feature release to 1.1.0 (CURRENT_PROJECT_VERSION 120).
• Check in the Mobbin-grounded product plan, focused tests, and six inspected iPhone 17 Pro runtime captures.

Related: #98, #99, #95

Product behavior

The shipped Phase 1 path is:

Welcome -> real home -> first item -> location -> review -> atomic save -> paywall -> created inventory

The optional Juniper House example remains deferred so it does not delay or contaminate activation data.

Validation

• Clean iPhone 17 Pro simulator build
• Unit: 18 passed, 0 failed
• UI/accessibility: 7 passed, 0 failed
• Runtime capture: 1 passed, 0 failed
• git diff --check: passed
• Xcode Cloud preflight: passed; no existing uploaded builds for 1.1.0

Residual risk

Live RevenueCat purchase/restore and real CloudKit synchronization were not exercised locally. The PR Xcode Cloud workflow should publish the branch build to TestFlight for device validation.