v0.2.0 — Multi-account, OAuth sign-in and credit statistics

Highlights

Multi-account management

• New Accounts tab: add several CodeBuddy accounts through OAuth QR-code / link sign-in (poll-based flow, no callback redirect).
• OAuth-added credentials live in $DSH_HOME/.codebuddy-cli-accounts.json; each account keeps its own token, expiry and identity.
• Listed accounts show which one is Current; switch or delete with one click. With no OAuth account the plugin still follows the CLI sign-in, so the original single-account behaviour is preserved.
• Per-account daily check-in with a checked-in badge.

Credit statistics

• New Credit statistics tab aggregating official request usage across accounts: remaining / today / 7-day / month summary, a daily stacked trend chart (hover a column for that day's per-model usage), a per-model breakdown, and a credit-package / request-usage detail panel.
• Each card carries its own account filter and range switch (30 days / today / 7 days / this month).

Cleanup

• The settings card body is now four tabs — Accounts, Available models, Credit statistics, Remaining credit.
• Dropped dead locale keys and realigned en/zh, removed an unused OAuth helper and its poll constants, and dropped an unused accounts-path export.
• README / README.en.md synced with the current UI.

Verification

• pnpm run check green: typecheck + 250 tests (248 passed, 1 skipped) + build.
• lib/ rebuilt so the bundled version literal reads 0.2.0.