PR A0: add identify() as backward-compat alias for addTraitsToUser() in useAnalytics

Part of #26686.

Add `identify()` as the canonical method name to `UseAnalyticsHook` and its implementation, keeping `addTraitsToUser` as a `@deprecated` alias.

**Branch**: `refactor/26686_a0-platform_identify-alias`
**PR**: #26807
**Status**: ✅ Done