[hanpeter]

Upgrades all frontend and backend dependencies, and bumps Poetry to 2.5.1 in CI and the Dockerfile.

Held back

• jsdom stays at 30.0.1. Version 30.1.1 made the LogForm and LogsPage tests flaky under coverage (4 of 10 runs failed, against 0 of 13 on 30.0.1). The range is still ^30.0.1, so the next upgrade retests it.
• pydantic-core stays at 2.46.5 because pydantic 2.13.5 pins it exactly.

Notes

• jest-dom has no Vitest 5 support yet (Vitest 5: matcher types are lost — Assertion<T> augmentation no longer merges with Vitest's Assertion<R, T> testing-library/jest-dom#738, fix in feat: support vitest 5 testing-library/jest-dom#742), so vitest-jest-dom.d.ts adds the matcher types through Vitest's Matchers interface. Delete it once jest-dom ships support. .vitest is now gitignored.
• fastapi 0.142 adds opentelemetry-api as a dependency.
• All GitHub Actions were already at their latest release.

Testing
Frontend build and coverage suite pass (261 tests, 100% on src/logic). Backend pycodestyle and pytest pass (266 tests, 100%) on Python 3.14, and CI covers 3.13. The Docker image builds and imports the upgraded packages.