BetterTrack App 0.55

• Idempotency-key adoption (#432) gated off — header 500s tx-create on prod (P1 filed) + search-bar inset fix

  Full client adoption of Idempotency-Key on the offline queue's mutation
  endpoints, reusing the persisted per-op clientId UUID (no schema change):
  header attached on tx-create + cash ops + value points, 409 IN_PROGRESS
  retried, 409 MISMATCH permanent, 400 KEY_INVALID regenerated once. Shipped
  behind SyncFeatureFlags.IDEMPOTENCY_KEYS_ENABLED=false: an on-device A/B
  proved the header itself turns POST /portfolios/{id}/transactions into a
  500 on prod (same body without it: 201) — evidence + timestamps in
  PLATFORM_ASKS.md #15; flip the flag when the platform fix ticks.

  Owner ask: asset-search bar no longer draws under the status bar
  (statusBarsPadding on the hand-rolled topBar Row).

  337 unit tests green (15 new, incl. MockWebServer wire-level header
  coverage).