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per-provider flag that chose between headless and plain HTTP is obsolete.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/CvSearchDbContext.cs

@@ -79,7 +79,6 @@ public sealed class CvSearchDbContext : DbContext
             entity.Property(x => x.InitialKeywordsJson).HasMaxLength(2000).HasDefaultValue("[]").IsRequired();
             entity.Property(x => x.MaxResults).HasDefaultValue(20);
             entity.Property(x => x.DisplayOrder).HasDefaultValue(0);
-            entity.Property(x => x.UseHeadlessBrowser).HasDefaultValue(false);
         });
     }
 }