fix: get all Playwright E2E tests loading and expand CI to run full suite (#6009)

## Fix Playwright E2E tests and expand CI to run full suite

### Problem

The full Playwright suite was broken in two ways:

1. **`ConvertE2E.spec.ts` crashed at import time** —
`conversionEndpointDiscovery.ts` imported a React hook at the top level,
which pulled in the entire component tree. That chain eventually
required `material-symbols-icons.json` (a generated file that didn't
exist), crashing module resolution before any tests ran.

2. **CI only ran cert validation tests** — both `build.yml` and
`nightly.yml` hardcoded `src/core/tests/certValidation` as the test
path, silently ignoring everything else.

### Changes

**`ConvertE2E.spec.ts` — complete rewrite**
The old tests were useless in practice: all 9 dynamic conversion tests
were permanently skipped unless a real Spring Boot backend was running
(they called a live `/api/v1/config/endpoints-enabled` endpoint at
module load time). Replaced with 4 focused tests that use `page.route()`
mocking — no backend required, same pattern as
`CertificateValidationE2E`.

New tests cover:
- Convert button absent before a format pair is selected
- Successful PDF→PNG conversion shows a download button (mocked API
response)
- API error surfaces as an error notification
- Convert button appears and is enabled after selecting valid formats

**`conversionEndpointDiscovery.ts` — deleted**
Only existed to support the old tests. The `useConversionEndpoints`
React hook it exported was never imported anywhere else.

**`ReviewToolStep.tsx`**
Added `data-testid="download-result-button"` to the download button —
required for the happy-path test assertion.

**CI workflows (`build.yml`, `nightly.yml`)**
- Added a `Generate icons` step before Playwright runs (`node
scripts/generate-icons.js`) — the icon JSON is generated by `npm run
dev` locally but skipped by `npm ci` in CI
- Removed the `src/core/tests/certValidation` path filter so the full
suite runs

.github/workflows/build.yml

@@ -236,10 +236,12 @@ jobs:
           cache-dependency-path: frontend/package-lock.json
       - name: Install frontend dependencies
         run: cd frontend && npm ci
+      - name: Generate icons
+        run: cd frontend && node scripts/generate-icons.js
       - name: Install Playwright (chromium only)
         run: cd frontend && npx playwright install chromium --with-deps
       - name: Run E2E tests (chromium)
-        run: cd frontend && npx playwright test src/core/tests/certValidation --project=chromium
+        run: cd frontend && npx playwright test --project=chromium
       - name: Upload Playwright report
         if: always()
         uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0

.github/workflows/nightly.yml

@@ -35,11 +35,14 @@ jobs:
       - name: Install frontend dependencies
         run: cd frontend && npm ci
 
+      - name: Generate icons
+        run: cd frontend && node scripts/generate-icons.js
+
       - name: Install all Playwright browsers
         run: cd frontend && npx playwright install --with-deps
 
       - name: Run E2E tests (all browsers)
-        run: cd frontend && npx playwright test src/core/tests/certValidation
+        run: cd frontend && npx playwright test
 
       - name: Upload Playwright report
         if: always()