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per-provider flag that chose between headless and plain HTTP is obsolete.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-matcher-api-models/Settings/JobSearchSettings.cs

@@ -21,8 +21,6 @@ public sealed class JobProviderConfig
     public string JobLinkContains { get; set; } = string.Empty;
     public List<string> InitialKeywords { get; set; } = [];
     public int MaxResults { get; set; } = 20;
-    /// <summary>When true the scraper uses a headless Chromium browser to render JS-heavy pages.</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.