Document Flutter Feature Flags initialization timeout

[leoromanovsky]

Motivation

Flutter applications need a documented upper bound for the first Feature Flags context initialization.

The Dart and Flutter SDKs now provide the same bounded initialization behavior as the iOS and Android SDKs.

Changes and Decisions

• Add timeout configuration to the Flutter-integrated, standalone Dart, and complete setup examples.
• Document the five-second default and the complete initialization pipeline covered by the timeout.
• Document FlagsInitializationTimeoutException, stored-assignment behavior, and late recovery.
• Keep the initialization timeout separate from the HTTP client timeout.
• Document datadog_flags and datadog_flags_flutter 1.1.0 as the first supported versions.

Merge readiness

• Ready for merge

This PR depends on DataDog/dd-sdk-flutter#1155 and publication of datadog_flags and datadog_flags_flutter 1.1.0.

AI assistance

Codex assisted with the initial draft and source comparison. The content was checked against SDK PR 1155 and the existing iOS and Android documentation.

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/leo.romanovsky/flutter-flags-initialization-timeout-docs/feature_flags/client/flutter