Flutter SDK 0.2.2 — Web sync and CustomerInfo policies

Flutter Web now delegates syncAttributesAndOfferingsIfNeeded() to the existing
JavaScript session and forwards all four CustomerInfo fetch policies. Flutter's
default is explicitly CACHED_OR_FETCHED; cache-only reads do not wait for HTTP.

• Preserve the provider's five-call rolling 60-second allowance, same-session
  cache fallback, failed-admission counting and retry timing.
• Keep network failures as failures while retaining the last valid snapshot and
  any successful customer refresh preceding an offerings failure.
• Mirror background updates with ordered snapshots and protect newer customer
  state from superseded or previous-account responses.
• Retain sanitized provider error codes (CACHE_MISS, RATE_LIMITED_NO_CACHE)
  and numeric retryAfterMillis, without copying raw error details.
• Require @inappifylabs/web-sdk 0.2.0 or newer; probe actual combined-sync support.
  Android remains pinned to Kotlin v0.2.1. Native purchase/cache/recovery behavior
  and existing public method signatures are unchanged.
• Update Web integration docs and the official agent skill for Flutter 0.2.2.

Validation: 408 Flutter SDK tests, 40 Chrome tests against the integrity-verified
published Web SDK 0.2.0 provider, and the example test pass. Dart analysis reports
no errors or warnings (existing informational lints remain). Browser tests use
controlled transport and clock inputs, with no live purchases or customer writes.