feat: add Cockpit account transfer compatibility

[icebear0828]

Summary

• add account import/export compatibility for Cockpit Tools, Sub2API, CPA, raw arrays, direct token fields, and text/plain token lines
• add remaining_percent normalization and cache successful single-account quota queries
• update Dashboard import/export handling and tracked README/CHANGELOG docs

Verification

• npm test -- tests/unit/services/account-transfer-formats.test.ts tests/unit/services/account-query.test.ts tests/unit/auth/quota-utils.test.ts tests/unit/routes/accounts-import-export.test.ts tests/unit/routes/shared/proxy-rate-limit.test.ts shared/account-transfer-client.test.ts
• cd web && npx vitest run src/components/AccountImportExport.test.tsx
• npm run build
• npm test

Notes

• docs/ is gitignored and project rules prohibit git add -f; the ignored docs were updated locally but are not included in this PR.
• Pre-existing local changes to config/default.yaml, AGENTS.md, and scripts/restart-tmux.sh were left out of the commit.