Add opt-in "write all data to Apple Health, automatically"

[BLABLA1000gg]

What this PR does

Adds an opt-in "Write all data to Apple Health, automatically" toggle to the iOS app.

Today the iOS HealthKitBridge already writes NOOP's core vitals (resting HR, HRV, blood oxygen, respiratory rate) back into Apple Health on every sync — and it already requests sleep-share permission in writeTypes, but never actually writes sleep. This PR closes that gap: with the toggle on, NOOP additionally mirrors its strap-detected sleep stages into Apple Health, on the same automatic syncs that already run (scenePhase-active and the live-delivery observers). No new consent prompt is needed because the sleep share scope was already being requested.

The toggle is off by default (privacy-first, matching the bridge's "strictly opt-in" ethos). When off, behaviour is unchanged — core vitals only. Recovery and Strain are NOOP-only scores with no Apple Health type, so they stay in NOOP; the toggle copy says so.

Changes

• Packages/StrandImport/…/NoopHealthSleepExport.swift — a pure, platform-agnostic parser that turns a session's stagesJSON into absolute-time stage intervals. Handles the computed segment-array format ([{start,end,stage}], mapping wake/light/deep/rem) and falls back to a single asleepUnspecified span for the imported minutes-dict or any undecodable JSON, so every night still lands. Stage-name mapping mirrors SleepView.decodeSegments exactly. Lives in StrandImport (not the iOS target) so it compiles everywhere and is unit-testable on the host.
• StrandiOS/Health/HealthKitBridge.swift — writeSleepBack emits sleepAnalysis category samples using the same HKMetadataKeyExternalUUID dedup + HKSource.default() scoping as the existing vitals write-back (re-syncing a night refreshes rather than duplicates, and never touches another app's sleep). It reads sleep from the computed (deviceId + "-noop") and imported ids and unions them, mirroring the vitals precedence. Gated behind a persisted writeAllData flag and run inside the same sync() round-trip, so a sleep-save failure surfaces in lastError and does not falsely advance lastSync.
• Strand/Screens/AppleHealthView.swift — a StrandDesign toggle in the authorized live-sync card, persisted under the bridge's key; switching it on kicks an immediate sync so the choice takes effect right away.

Type of change

• New feature

How it was tested

Not a BLE-path change. Verified locally on macOS with Xcode 26.6 (iOS 26.5 SDK):

• swift test in Packages/StrandImport — added NoopHealthSleepExportTests (6 cases: segment-array decoding with absolute times + stage mapping, unknown-stage/zero-span skipping, imported-dict fallback, nil/empty/garbage JSON fallback, degenerate span). All pass.
• Full NOOPiOS app module compiles against the real HealthKit SDK (swiftc emits NOOP.swiftmodule, 0 errors, no new warnings). The whole SwiftPM dependency graph also compiles for iOS. (A local end-to-end simulator run wasn't possible on this machine — the freshly-installed simulator runtime wouldn't mount — but that's asset/link packaging, not the code; the App-build CI does the full build.)

I don't have a paired WHOOP strap + iPhone to observe the samples land in the Health app end-to-end, so a maintainer with hardware confirming the sleep samples appear (and dedupe on re-sync) would be appreciated.

Checklist

• Swift package tests pass for any package I touched (swift test in Packages/StrandImport)
• Android unit tests pass if I touched android/ (N/A — no android/ changes)
• No new build warnings introduced
• UI changes use only StrandDesign tokens — no hardcoded colors, fonts, or spacing
• No hardcoded hex frame bytes; protocol facts live in the schema / decoders (N/A)
• Follows the conventions in docs/CONTRIBUTING.md
• I did not commit generated output (Strand.xcodeproj/) or any secrets/keystores

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