deps(deps): bump sherpa-onnx in the production-dependencies group

Bumps the production-dependencies group with 1 update: [sherpa-onnx](https://github.com/k2-fsa/sherpa-onnx).


Updates `sherpa-onnx` from 1.12.23 to 1.12.25
- [Release notes](https://github.com/k2-fsa/sherpa-onnx/releases)
- [Changelog](https://github.com/k2-fsa/sherpa-onnx/blob/master/CHANGELOG.md)
- [Commits](k2-fsa/sherpa-onnx@v1.12.23...v1.12.25)

---
updated-dependencies:
- dependency-name: sherpa-onnx
  dependency-version: 1.12.25
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: production-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

local_ai_server/requirements.txt

@@ -3,7 +3,7 @@ vosk==0.3.45
 llama-cpp-python==0.3.16
 piper-tts==1.2.0
 numpy==1.26.4
-sherpa-onnx==1.12.23
+sherpa-onnx==1.12.28
 kokoro>=0.9.2
 # Note: numpy is used by both Piper TTS and Kroko/Sherpa STT (PCM16→float32 conversion)
 # sherpa-onnx provides local streaming ASR (Kroko is built on sherpa-onnx)