Implement hooks

[mschoenlaub]

This SDK does not support lifecycle hooks. This should change.

[technicalpickles]

Spec for reference: https://openfeature.dev/docs/reference/concepts/hooks

[josecolella]

Implementation PR: #214

This adds the full hooks lifecycle per OpenFeature spec section 4, including:

• Hook interface module with default no-op stages
• HookContext class with immutable/mutable field semantics
• HookExecutor for lifecycle orchestration with proper ordering and error isolation
• Client integration with hooks/hook_hints parameters on all evaluation methods
• No-hooks fast path for zero-overhead when hooks aren't registered
• Comprehensive unit and spec compliance tests (320 examples, 0 failures)

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