Fix rnnoise only works with 48khz audio

[bmatherly]

This change converts the sampling frequency to whatever was requested by the consumer. It also improves a rare underflow condition in the filter and uses fake samples to fill the gap.

[Copilot]

Pull request overview

This PR updates the RNNoise module so it can operate internally at RNNoise’s required 48 kHz while returning audio at the consumer-requested sampling rate, and it improves handling of a rare short-output (“underflow”) scenario by synthesizing an extra padded chunk and carrying excess forward.

Changes:

• Always request/process RNNoise audio at 48 kHz float, then resample back to the originally requested sampling rate.
• Add logic to mitigate rare output shortfalls by processing an extra zero-padded RNNoise block and storing excess in carry buffers.
• Manage a lazily-created resample filter instance and close it during teardown.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/modules/rnnoise/link_rnnoise.c	Resamples link output back to the consumer-requested frequency after RNNoise processing and ensures proper cleanup.
src/modules/rnnoise/filter_rnnoise.c	Adds resampling-back support in the filter path and introduces extra-chunk padding to reduce zero-fill underflows.