feat(cv-search-job): enrich diagnostics and add scan summary to results email

Add funnel-level logging to HtmlJobSearcher (total anchors found,
stage-1 href-filter count, stage-2 keyword-filter count) and warn
when the keyword list is empty. Log the full search URL and response
size to catch silent HTTP failures or bot-block pages.

In CvSearchJobTask, log keywords and active providers at session start,
per-provider URL counts after each scrape, and every scored URL with its
verdict (ACCEPTED / rejected) at Information level.

Add a scan summary block to the results email (both non-empty and
empty-results paths) showing the CV keywords used as chips and the
comma-separated list of providers scanned.

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

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

@@ -35,12 +35,16 @@ public sealed class CvSearchEmailSender
     /// <param name="toEmail">Primary recipient (the user who triggered the search).</param>
     /// <param name="attachmentFileName">Relative filename of the CV PDF to attach, or <c>null</c>.</param>
     /// <param name="results">Ranked list of job search results to include in the email body.</param>
+    /// <param name="keywords">CV keywords used to drive the job search.</param>
+    /// <param name="providerNames">Names of the providers that were scanned.</param>
     /// <param name="language">Two-letter language code for template rendering.</param>
     /// <param name="ct">Cancellation token.</param>
     public async Task SendResultsAsync(
         string toEmail,
         string? attachmentFileName,
         IReadOnlyList<JobSearchResultEntity> results,
+        IReadOnlyList<string> keywords,
+        IReadOnlyList<string> providerNames,
         string language,
         CancellationToken ct)
     {
@@ -54,7 +58,7 @@ public sealed class CvSearchEmailSender
 
         if (recipients.Count == 0) return;
 
-        var htmlBody = BuildBody(results, language);
+        var htmlBody = BuildBody(results, keywords, providerNames, language);
         var subject = _emailTemplates.Render("email.search-results.subject", language,
             ("count", results.Count.ToString()));
 
@@ -81,11 +85,14 @@ public sealed class CvSearchEmailSender
     /// <summary>
     /// Renders the HTML email body from the results list.
     /// Returns the empty-results template when no results are present.
+    /// Prepends a scan summary block showing the keywords and providers used.
     /// </summary>
-    private string BuildBody(IReadOnlyList<JobSearchResultEntity> results, string language)
+    private string BuildBody(IReadOnlyList<JobSearchResultEntity> results, IReadOnlyList<string> keywords, IReadOnlyList<string> providerNames, string language)
     {
+        var scanSummary = BuildScanSummary(keywords, providerNames);
+
         if (results.Count == 0)
-            return _emailTemplates.Get("email.search-results.empty", language);
+            return scanSummary + _emailTemplates.Get("email.search-results.empty", language);
 
         var items = new System.Text.StringBuilder();
         for (int i = 0; i < results.Count; i++)
@@ -107,7 +114,29 @@ public sealed class CvSearchEmailSender
 
         return _emailTemplates.Render("email.search-results.body", language,
             ("count", results.Count.ToString()),
-            ("items", items.ToString()));
+            ("items", scanSummary + items.ToString()));
+    }
+
+    /// <summary>
+    /// Builds the scan summary block showing the CV keywords and providers used for the search.
+    /// </summary>
+    private static string BuildScanSummary(IReadOnlyList<string> keywords, IReadOnlyList<string> providerNames)
+    {
+        var keywordsHtml = keywords.Count > 0
+            ? string.Join("", keywords.Select(k =>
+                $"<span style=\"display:inline-block;background:#e9ecef;border-radius:4px;padding:2px 8px;margin:2px;font-size:12px\">{k}</span>"))
+            : "<span style=\"color:#6c757d;font-size:12px;font-style:italic\">none detected</span>";
+
+        var providersText = providerNames.Count > 0
+            ? string.Join(", ", providerNames)
+            : "none";
+
+        return $"""
+            <div style="background:#f8f9fa;border:1px solid #dee2e6;border-radius:6px;padding:14px 16px;margin-bottom:18px;font-size:13px;color:#495057">
+              <div style="margin-bottom:8px"><strong>Keywords used:</strong>&nbsp;{keywordsHtml}</div>
+              <div><strong>Providers scanned:</strong>&nbsp;{providersText}</div>
+            </div>
+            """;
     }
 
     /// <summary>