feat(providers): add headless browser scraping via Playwright for SPA job sites

ejobs.ro migrated to a Nuxt SPA - plain HTTP GET returns only the JS
bundle. This change equips cv-search-job with a headless Chromium
(Playwright 1.60) so it can fully render SPA pages before extracting
job links.

- Add UseHeadlessBrowser flag to JobProviderEntity, JobProviderConfig,
  and CvSearchDbContext; map it in JobTokenService.ToConfig so the flag
  is included in the session provider-config snapshot
- Migration: add UseHeadlessBrowser column; fix ejobs.ro search URL
  (remove /user/ prefix that caused 404) and set UseHeadlessBrowser=true
- HtmlJobSearcher: detect flag and dispatch to FetchWithPlaywrightAsync;
  plain-HTTP path is unchanged; NetworkIdle timeout falls back to partial
  content rather than failing outright
- Dockerfile: download Playwright Chromium in the SDK build stage via
  npx; copy browser binaries to the final image; install Chromium system
  libs (Ubuntu noble t64 variants)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Jobs/cv-search-job/Dockerfile

@@ -29,9 +29,28 @@ COPY Helpers/startup-helpers/ Helpers/startup-helpers/
 
 RUN dotnet publish Jobs/cv-search-job/cv-search-job.csproj -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false
 
+# Download Playwright Chromium browser in the build stage.
+# Node.js is only needed here to run npx — it is not copied to the final image.
+ENV PLAYWRIGHT_BROWSERS_PATH=/ms-playwright
+RUN apt-get update && apt-get install -y --no-install-recommends nodejs npm \
+    && npx --yes playwright@1.60.0 install chromium \
+    && rm -rf /var/lib/apt/lists/*
+
 FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS final
 WORKDIR /app
 
+# System libraries required by Chromium on Debian bookworm
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libnss3 libnspr4 libatk1.0-0 libatk-bridge2.0-0 libcups2 libdrm2 \
+    libxkbcommon0 libxcomposite1 libxdamage1 libxfixes3 libxrandr2 \
+    libgbm1 libasound2t64 libpango-1.0-0 libcairo2 libatspi2.0-0 \
+    libwayland-client0 libx11-xcb1 libx11-6 libxcb1 libxext6 \
+    && rm -rf /var/lib/apt/lists/*
+
+# Copy the Playwright Chromium browser from the build stage
+ENV PLAYWRIGHT_BROWSERS_PATH=/ms-playwright
+COPY --from=build /ms-playwright /ms-playwright
+
 COPY --from=build /app/publish .
 
 ENTRYPOINT ["dotnet", "cv-search-job.dll"]