feat(usage): Usage Settings Overhaul

[boggedbrush]

Summary

• add a dedicated Settings > Usage section with shared provider usage rendering
• improve Claude usage plan/reset handling, including derived 5-hour reset fallback
• add a compact chat composer usage widget with smoother docking/animation behavior

Screenshots

Usage settings page

Chat usage widget

Validation

• bun fmt
• bun lint
• bun typecheck

[boggedbrush]

Re-validated on a fresh merge commit against main on April 20, 2026.

Confirmed locally:

• bun install
• bun dev:server -- --no-browser
• bun fmt
• bun lint
• bun typecheck

This PR is working and able to merge.