fix(monitoring): handle SQLite token statistics errors

[mameikagou]

Overview

Fixes #2468.

• allow the existing SQLite monitoring bucket query to use the safe strftime function;
• display the backend msg from plain API error objects instead of [object Object];
• add focused backend and frontend regressions.

Screenshots

No layout change. Error text changes from:

[object Object]

to the backend-provided message.

Validation

• uv run pytest tests/unit_tests/persistence/test_tenant_uow.py -q --tb=short --capture=no — 117 passed
• uv run ruff check and uv run ruff format --check on changed Python files
• node --test tests/unit/*.test.mjs — 35 passed
• pnpm exec tsc --noEmit
• pnpm lint — 0 errors
• pnpm build
• git diff --check

Checklist

• Read the contribution guide
• I have signed, or will sign when prompted by the CLA bot
• Communicated with the maintainer in [Bug]: 仪表盘监控token数据失败返回[object Object] #2468 (comment)
• Tested the change locally

[github-actions]

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[RockChinQ]

Hi @mameikagou , please sign the CLA before we can merge this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[dadachann]

Thanks for the focused diagnosis and proposed fix. We independently reimplemented and merged the repair in #2479 because this PR could not pass the CLA gate. Closing this as superseded.