Link pageFetcher.PageFetches to cvSearch.JobSearchSessions

Adds nullable JobSearchSessionId to PageFetchEntity and FetchPageRequest.
cv-search-job passes session.Id on every fetch so all Playwright page
loads for a job search session can be traced back to their session.
Includes index on JobSearchSessionId for efficient lookup.

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

Apis/page-fetcher-data/Data/Entities/PageFetchEntity.cs

@@ -31,4 +31,10 @@ public sealed class PageFetchEntity : BaseEntity
 
     /// <summary>Exception message when <see cref="Success"/> is <c>false</c>.</summary>
     public string? ErrorMessage { get; set; }
+
+    /// <summary>
+    /// Optional reference to the <c>cvSearch.JobSearchSessions</c> row that triggered this fetch.
+    /// Null for fetches not originating from a job search session (e.g. direct CV-to-job matches).
+    /// </summary>
+    public string? JobSearchSessionId { get; set; }
 }