iOS development - Privacy-Centric iOS Paraphrasing Keyboard App

I want a lightweight iOS app that rewrites user input based on tone — Professional Mode for formal/business use and Creative Mode for witty, casual rephrasing. The app must be privacy-first, ideally working fully offline, using an on-device model Nous-Hermes-2-Mistral-7B-DPO.Q2_K.gguf whic works great . No cloud logging, no analytics — just clean UI and fast local AI.

Functional requirements:

1. Login / sign up for pricing subscriptions, first 3 usage for free and then charge them $5/month.
2. Keyboard must be elegant like default iOS just with 3 extra buttons , formal, creative and undo to undo text
3. Keyboard must only paraphrase the selected text
4. Upload on App Store