Remove ElevenLabs enum namespace and global config

[renal128]

Summary

The SDK is imported as ElevenLabs, but it also has a public ElevenLabs enum. This causes issues when the consumer app wants to use qualified name like ElevenLabs.Message, because ElevenLabs gets resolved to the ElevenLabs enum. This PR removes the enum and moves its parts to appropriate places.

• Delete the shadowing public enum ElevenLabs and move Events under Public/Conversation/Events
• Promote LogLevel, AgentState, and a single public version to module-level API
• Replace ElevenLabs.configure with ConversationClient(logLevel:)

Test plan

• swift build

Stacked on #221

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Note

Medium Risk
This is a breaking public API change: consumers must replace ElevenLabs.configure, nested ElevenLabs.AgentState/LogLevel, and ElevenLabs.version with module-level types and ConversationClient(logLevel:). Runtime behavior is mostly organizational aside from per-client instead of global log configuration.

Overview
Removes the public ElevenLabs enum so the module name no longer shadows types like Message when apps use qualified names (ElevenLabs.Message). AgentState, LogLevel, and version are now top-level public API; generated Version.swift exposes public let version instead of internal SDKVersion.

Global ElevenLabs.configure and Configuration are deleted. Logging is configured per ConversationClient(logLevel:), which passes logLevel into Dependencies when starting a session. Docs (README, Usage) are updated accordingly.

Internal code drops ElevenLabs. prefixes on AgentState / LogLevel; token and conversation init payloads still send SDK version via the new version constant.

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