prevent panic on paraformer engine init failure

[AdityaShome]

Description

This PR fixes a critical bug where the dora-funasr-mlx node would panic and silently crash the entire voice chat dataflow if the Paraformer ASR engine failed to initialize (e.g., due to missing MLX models or out-of-memory errors).
Because Dora does not automatically restart nodes when they panic, this would cause the UI to remain stuck in the "running" state without any transcription ever arriving.
Fixes: #34

Changes Made

• Replaced the panicking unwrap() on the lazily initialized engine at node-hub/dora-funasr-mlx/src/main.rs:103 with a safe match block.
• Added a log::error! message and a send_log() Dora event to inform the user.
• Used continue to safely skip the audio frame if the engine is unavailable, keeping the node alive so it doesn't crash the dataflow.

Testing

• Code structurally verified to gracefully handle None.
• cargo fmt passed cleanly.