feat: add personalization API (run/runAll) to Flutter SDK

[devin-ai-integration]

Summary

Adds run() and runAll() to the existing ReelevantAnalytics class so the same SDK instance handles both analytics tracking and personalization — with shared identity.

Key design: Identity auto-resolves from setUser() → stored tmpId → fallback, so callers don't pass userId manually (but can override via RunOptions.userId).

New API surface

ReelevantAnalytics(
    companyId: '...',
    datasourceId: '...',
    runnerUrl: 'https://reelevant.run',      // default
    runnerTimeout: Duration(seconds: 5),      // default
    fallback: FallbackStrategy.empty,         // default
)

Future<RunResult> run(RunOptions options)
Future<List<RunResult>> runAll(List<RunOptions> optionsList)

RunResult.body uses subclasses: JsonRunContent, HtmlRunContent, ImageRunContent, EmptyRunContent.

Files

• New: lib/reelevant_client.dart — types (RunOptions, RunResult, RunContent subclasses, FallbackStrategy, error classes) + internal runner HTTP logic using the existing http.Client
• Modified: lib/reelevant_analytics.dart — added run()/runAll()/_resolveUserId()/_handleRunError() methods + new constructor params with defaults + re-exports reelevant_client.dart
• Updated: README.md — full personalization docs with usage examples

Link to Devin session: https://app.devin.ai/sessions/cb78c8f2e2ba4d348b6f9a8c274c69bb
Requested by: @vmarchaud

[devin-ai-integration]

Original prompt from vmarchaud

i want to provide the same DX as the web sdk but for mobile SDKs, check mobile personalization part in the docs to understand better

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Devin Review found 3 potential issues.