[lcfeaturecontrol-review-fixes] Fix JWT log leak, drop macOS/tvOS, coalesce requests

- FeatureControlManager/NotificationsClient: pass debug: false at every
  api.request(...) call site — the API default (debug: true) was printing
  Authorization: Bearer <jwt> on every request, release builds included.
- Package.swift: drop macOS/tvOS from platforms — LCEssentials.API (used by
  LCFeatureControl) is iOS/watchOS-only and the vendored xcframework has no
  macOS/tvOS slice.
- FeatureControlManager: coalesce concurrent evaluate() calls on a cold cache
  into a single in-flight request per key instead of firing one per caller.
- FeatureControlManager/NotificationsClient: treat a 200 response carrying
  {"error": true} as a failure instead of caching/returning it as success.
- FeatureControlNotificationsClient: thread a cursor param through list() so
  the already-decoded nextCursor can actually be used to page.
- Tests: 9 new tests (coalescing, envelope-error-on-200, cursor param, a real
  object payload decoded through a full evaluate response, date-decode
  failures) and removed the 7 remaining force-unwraps in test scaffolding.
- Documentation/FeatureControl.md: new guide for the LCFeatureControl product,
  cross-linked from README.md and Extensions.md.

README.md

@@ -35,6 +35,7 @@ import LCEssentials
 | **[Extensions.md](Documentation/Extensions.md)** | Foundation / value-type / string / collection / numeric / date / crypto extensions and the `LCEssentials` namespace |
 | **[SwiftUI.md](Documentation/SwiftUI.md)** | SwiftUI components (`LCENavigationView`) and `View` helpers |
 | **[UIKit.md](Documentation/UIKit.md)** | Programmatic layout & constraints, view/control extensions, navigation, tables, and drop-in components (`LCSnackBarView`, image picker/zoom, GIF loading) |
+| **[FeatureControl.md](Documentation/FeatureControl.md)** | `LCFeatureControl` — Atomenta Feature Control client: flag evaluation, cache/safe-degrade, notifications inbox, exposure telemetry |
 
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