ci: add QA workflows and tests for scraper and Vue UI

[VikramAditya33]

This PR implements the CI/QA wiring for the new Vue.js UI and aligns the project’s workflows with the patterns used in other openZIM projects (Mindtouch, freecodecamp). It also adds Prettier and ESLint to pre-commit and ensures Vitest is correctly wired with a minimal smoke test.

Changes

• QA workflow split (.github/workflows/QA.yaml)

• Rename the single check-qa job into two jobs:

• check-scraper-qa: runs Black, Ruff, and Pyright on the Python scraper (same behavior as before).

• check-zimui-qa: new job for the Vue UI that:

1. Sets up Node.js 20.
2. Installs dependencies in ui/ via npm ci.
3. Runs Prettier in check mode on ui/src (npx prettier --check src/).
4. Runs ESLint via npm run lint.

• Tests workflow split (.github/workflows/Tests.yaml)

• Split the monolithic tests into four jobs:

• test-scraper: runs Python tests with coverage and uploads to Codecov (using codecov/codecov-action@v5).

• build-scraper: ensures the scraper can be built as sdist + wheel.

• build-and-test-zimui: new job for the Vue UI that:

1. Sets up Node.js 20.
2. Installs dependencies in ui/ via npm ci.
3. Runs npm run test:unit.
4. Builds the UI with npm run build.

• build_docker: unchanged Docker image build + run check for the scraper image.

• Pre-commit configuration (.pre-commit-config.yaml)

• Add Prettier mirror:

• prettier hook targeting ui/ files (files: ui\/.*$).

• Add ESLint mirror:

• eslint hook targeting ui/src JS/TS/Vue files:

• files: ui\/src\/.*(?:\.[jt]sx?|\.vue)$

• Uses ui/.eslintrc.cjs as config.

• Keep existing Python hooks (pre-commit-hooks, Black, Ruff, Pyright) unchanged.

• Vitest wiring (ui/src/utils/__tests__/placeholder.test.ts)

• Convert the placeholder test into a minimal but valid Vitest suite:

• Import describe, it, expect from vitest.

• Keep a simple “always true” test so the test pipeline is exercised.

• Intention is to keep this as a temporary smoke test and add real unit tests in a follow‑up issue.

Fixes #362.