Harden Core Data mapping against duplicate UUID crash loops

[barronlroth]

Parent: #82
Related: #81

Problem

CoreDataAppRepository builds home and location lookup dictionaries with Dictionary(uniqueKeysWithValues:). If CloudKit import, migration retry, or partial share state ever leaves duplicate CDHome.id or CDStorageLocation.id values in the local store, this call traps instead of throwing.

That is a plausible persistent launch/use crash-loop vector because AppStore.refresh() runs during app startup and refreshes again after remote changes.

Proposed work

• Replace Dictionary(uniqueKeysWithValues:) in repository mapping with duplicate-aware grouping.
• Log duplicate entity type, UUID, objectID URI, and persistent store scope.
• Pick a deterministic survivor for UI mapping or skip ambiguous records without crashing.
• Decide whether duplicate records should be repaired automatically or only surfaced as diagnostics.
• Add regression tests that insert duplicate home/location UUIDs and prove listHomes(), listLocations(), and AppStore.refresh() do not trap.

Acceptance criteria

• Duplicate Core Data UUIDs cannot crash the app during refresh or launch.
• Duplicate state produces actionable logs.
• Tests cover duplicate homes and duplicate locations across private/shared-store style data.