Add local usage analytics to Settings

[FuJacob]

Summary

generated by ai, please feel free to be flexible with implementation, this is just a starting point

Add a local analytics section to the Settings UI so users can see how much value they are getting from Cotabby, such as accepted completions and accepted words.

Motivation

Users currently have little visibility into whether autocomplete is helping them. A lightweight stats view can make Cotabby feel more tangible and can also help users debug suggestion quality without exposing private text.

Scope

• Add a Settings section or pane for local usage analytics.
• Track accepted suggestion count.
• Track accepted word count and/or character count.
• Show useful time ranges such as all time, last 7 days, and last 30 days if the storage model supports it.
• Include a clear reset/delete stats action.
• Keep all analytics local to the device.
• Do not store raw accepted text, prompts, OCR, app content, screenshots, or document contents.
• Consider whether breakdowns by backend, app, or suggestion type are useful without creating privacy risk.

Acceptance Criteria

• Users can open Settings and see accepted suggestion/word stats.
• Accepting a suggestion updates the counters reliably.
• Stats survive app restart.
• Users can reset the stored stats.
• Unit tests cover counter updates, persistence/reset behavior, and any pure date bucketing logic.
• No hosted analytics dependency is introduced.

Notes

Cotabby is local-first, so this should be framed as user-visible local usage stats rather than product telemetry.