⚡ Bolt: Centralize Foundation formatters to avoid expensive allocations

[acebytes]

💡 What: Replaced all inline instantiations of ByteCountFormatter and ISO8601DateFormatter with shared static instances.
🎯 Why: Instantiating formatters is computationally expensive in Swift. Reusing them avoids repeated allocation overhead, especially in UI updates and loops.
📊 Impact: Eliminates redundant formatter allocations during state updates, lowering memory pressure and improving UI responsiveness.
🔬 Measurement: Verify tests pass.

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PR created automatically by Jules for task 9348143352197494619 started by @acebytes

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Avoid sharing non-Sendable formatters across actors

ByteCountFormatter and ISO8601DateFormatter are non-Sendable reference types, so putting them in process-wide static properties creates shared mutable state that is accessed from different isolation domains (for example, @MainActor UI formatting in CacheoutViewModel and background cleanup logging in CacheCleaner). During a cleanup run these calls can overlap, which risks formatter races (incorrect output or crashes) and already trips Swift 6 concurrency diagnostics for unsafe global state. Prefer actor-local instances, @MainActor isolation, or explicit synchronization instead of a global singleton formatter.

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