identify() should accept IFlagsmithTrait for traits parameter (parity with setTraits)

## Problem

`flagsmith.identify()` accepts traits as `Record` where `IFlagsmithValue = string | number | boolean | null`, while `flagsmith.setTraits()` accepts `Record` where `IFlagsmithTrait = IFlagsmithValue | TraitEvaluationContext`.

This means you can't pass a `TraitEvaluationContext` (e.g. transient traits) via `identify()` — you have to call `identify()` first, then `setTraits()` separately.

## Expected behaviour

`identify()` should accept `IFlagsmithTrait` for traits, matching `setTraits()`:

```typescript
// Currently:
identify: (userId: string, traits?: Record) => Promise;

// Should be:
identify: (userId: string, traits?: Record) => Promise;
```

## Notes

- The runtime implementation in `flagsmith-core.ts` **already handles** `TraitEvaluationContext` in `identify()` via the `isTraitEvaluationContext()` type guard — this is purely a type definition fix.
- Change is in `types.d.ts` line 231.

Reported by a customer.