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>

Apis/cv-search-data/Data/Entities/JobProviderEntity.cs

@@ -30,4 +30,7 @@ public sealed class JobProviderEntity
 
     /// <summary>Controls display ordering in future admin UIs.</summary>
     public int DisplayOrder { get; set; }
+
+    /// <summary>When true, the scraper renders the page with headless Chromium instead of a plain HTTP GET.</summary>
+    public bool UseHeadlessBrowser { get; set; }
 }