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per-provider flag that chose between headless and plain HTTP is obsolete.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>

Jobs/cv-search-job/Services/HtmlJobSearcher.cs

@@ -72,7 +72,6 @@ public sealed class HtmlJobSearcher
         var fetchResponse = await _pageFetcher.FetchAsync(new FetchPageRequest
         {
             Url = searchUrl,
-            WaitFor = provider.UseHeadlessBrowser ? "networkidle" : "domcontentloaded",
             CallerService = "cv-search-job"
         }, ct);