[FR] Local inference for mobile app using llama.cpp

### Description

I would like to suggest implementing an option to use local LLM inference on mobile devices using llama.cpp library and either user provided or by the app downloaded quantized GGUF variant of LLM model. I believe such function would be feasible, since most middle tier mobile phones nowadays are capable of running usually a Q4_K_M quantization (the medium balanced quality/speed option) of 7B variants of many models at slower than PC, but bearable speed.

### Impact

Implementing this would benefit users who are not always able to access internet on their mobile devices, plus those who would wish a privacy of local LLM on the go.

### Additional Context

Inspired by addition of local inference option into desktop version of AppFlowy.

The issue names llama.cpp and references the desktop version's local inference as context, but identifies no mobile files, tests, or entry points. Start by examining the desktop implementation and the mobile app architecture. Done would mean a defined mobile local-inference option using user-provided or downloaded quantized models, with its scope and validation criteria established.

Written by the indexing model from the issue text.