feat(telnyx): add Telnyx assistant server framework

[lucasassisrosa]

Add Telnyx hosted AI Assistant as a first-class EVA framework alongside the existing Pipecat pipeline. The Telnyx provider connects to the Telnyx AI gateway via direct anonymous WebRTC (Verto JSON-RPC over WebSocket), bridges audio between the EVA user simulator (Twilio mulaw frames) and the Telnyx assistant (PCM 16 kHz), and enriches the audit log from the Telnyx Conversations API after the call ends.

New files:

• src/eva/assistant/base_server.py AbstractAssistantServer: template-method base class that defines the EVA server contract (FastAPI WebSocket endpoint, audio bridging, tool execution via ToolExecutor, audit log, audio recording, save_outputs). Concrete servers implement start() and _shutdown(); the base handles stop(), output saving, and artifact generation.

• src/eva/assistant/audio_bridge.py Audio format conversion utilities: mulaw 8 kHz ↔ PCM 16-bit 24 kHz resampling (libsoxr), PCM mixing, Twilio FrameSerializer protocol helpers, and framework/metrics log writers.

• src/eva/assistant/telnyx_server.py TelnyxAssistantServer(AbstractAssistantServer): the main server. - TelnyxAssistantManager: REST CRUD for benchmark assistants. - TelnyxDirectSessionConfig: dataclass for WebRTC session params. - TelnyxVertoJsonRpcClient: Verto JSON-RPC over WebSocket. - TelnyxWebRTCClient: aiortc RTCPeerConnection + media management. - TelnyxAssistantServer: bridges EVA Twilio frames to Telnyx WebRTC, handles conversation events, tool calls, dynamic variables, audit-log enrichment from Conversations API.

• src/eva/utils/audio_utils.py save_pcm_as_wav() helper shared by all server implementations.

• tests/unit/assistant/test_telnyx_server.py (20 tests)

• tests/unit/assistant/test_audio_bridge.py (3 tests)

Modified:

• src/eva/models/config.py: Add framework field to RunConfig.
• src/eva/orchestrator/worker.py: Add _get_server_class() dispatch.
• pyproject.toml: Add aiortc, aiohttp, soxr dependencies.

Addresses VSDK-277 review: adds the missing Python EVA wrapper that subclasses AbstractAssistantServer, registers in worker.py, routes tool calls through ToolExecutor, and produces all required EVA artifacts.