Remove UseHeadlessBrowser from JobProvider — all fetches now go via page-fetcher-api

page-fetcher-api always uses Playwright (networkidle by default), so the
per-provider flag that chose between headless and plain HTTP is obsolete.

- Removed from JobProviderEntity, CvSearchDbContext, JobProviderConfig, JobTokenService
- HtmlJobSearcher no longer passes WaitFor (uses page-fetcher-api default)
- EF migration drops the column from cvSearch.JobProviders

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

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

@@ -31,9 +31,6 @@ 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; }
-
     /// <summary>
     /// When false, the Stage 2 anchor-text keyword filter is skipped.
     /// Set to false for providers whose search URL already filters by relevance server-side (ejobs.ro, bestjobs.eu).