fix: stabilize and harden voice sessions

[Scoteezy]

Summary

• upgrade the ElevenLabs React and React Native SDKs together with the compatible LiveKit/WebRTC stack
• replace the shared mutable conversation wrapper with a lifecycle adapter that serializes start/stop, waits for disconnect, and resets the provider before reuse
• remove the obsolete audio API integration and LiveKit/audio patches
• harden server token parsing, external request failures, RevenueCat entitlement windows, and paginated ElevenLabs usage accounting
• add regression coverage for repeated sessions, teardown races, token parsing, quota boundaries, caching, and lifetime entitlements
• update voice quota and deployment documentation

Validation

• pnpm --dir packages/happy-app test --run sources/realtime/RealtimeSession.test.ts sources/realtime/RealtimeVoiceSessionAdapter.test.ts — 10 passed
• pnpm --dir packages/happy-server test --run sources/app/api/routes/voiceRoutes.test.ts sources/app/api/routes/voiceToken.test.ts — 26 passed
• pnpm --dir packages/happy-app typecheck
• pnpm --dir packages/happy-server typecheck
• APP_ENV=development pnpm --filter happy-app exec expo config --type prebuild
• pnpm install --offline --frozen-lockfile --ignore-scripts
• git diff --check

Manual test

A fresh native development build is required because the React Native SDK and native audio stack changed. Device soak testing should repeat start -> connected -> stop -> start with the public debug agent.