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/HtmlJobSearcher.cs

@@ -44,19 +44,27 @@ public sealed class HtmlJobSearcher
             .ToList();
 
         if (allKeywords.Count == 0)
+        {
+            _logger.LogWarning("Provider {Provider}: no keywords available (CV keywords empty, InitialKeywords empty), skipping", provider.Name);
             return [];
+        }
 
         var keywordsEncoded = HttpUtility.UrlEncode(string.Join(" ", allKeywords));
         var searchUrl = provider.SearchUrlTemplate.Replace("{keywords}", keywordsEncoded);
 
+        _logger.LogInformation(
+            "Provider {Provider}: fetching {Url} | CV keywords: [{Keywords}]",
+            provider.Name, searchUrl, string.Join(", ", cvKeywords));
+
         string html;
         try
         {
             html = await _http.GetStringAsync(searchUrl, ct);
+            _logger.LogInformation("Provider {Provider}: received {Length} chars of HTML", provider.Name, html.Length);
         }
         catch (Exception ex)
         {
-            _logger.LogWarning(ex, "Failed to fetch search results from {Provider} at {Url}", provider.Name, searchUrl);
+            _logger.LogWarning(ex, "Provider {Provider}: HTTP fetch failed for {Url}", provider.Name, searchUrl);
             return [];
         }
 
@@ -68,7 +76,11 @@ public sealed class HtmlJobSearcher
         var anchorPattern = new Regex(@"<a[^>]+href=[""']([^""']+)[""'][^>]*>(.*?)</a>",
             RegexOptions.IgnoreCase | RegexOptions.Singleline);
 
-        foreach (Match match in anchorPattern.Matches(html))
+        var allAnchors = anchorPattern.Matches(html);
+        var stage1Pass = 0;
+        var stage2Pass = 0;
+
+        foreach (Match match in allAnchors)
         {
             if (results.Count >= provider.MaxResults) break;
 
@@ -78,9 +90,18 @@ public sealed class HtmlJobSearcher
             if (!href.Contains(provider.JobLinkContains, StringComparison.OrdinalIgnoreCase))
                 continue;
 
+            stage1Pass++;
+
             // Stage 2: anchor text must contain at least one CV keyword
             if (!cvKeywords.Any(k => anchorText.Contains(k, StringComparison.OrdinalIgnoreCase)))
+            {
+                _logger.LogDebug(
+                    "Provider {Provider}: stage-2 reject | href={Href} | text={Text}",
+                    provider.Name, href, anchorText.Length > 100 ? anchorText[..100] : anchorText);
                 continue;
+            }
+
+            stage2Pass++;
 
             // Make absolute URL
             if (!Uri.TryCreate(href, UriKind.Absolute, out var absoluteUri))
@@ -95,7 +116,10 @@ public sealed class HtmlJobSearcher
                 results.Add(url);
         }
 
-        _logger.LogInformation("Provider {Provider}: found {Count} job URLs", provider.Name, results.Count);
+        _logger.LogInformation(
+            "Provider {Provider}: {TotalAnchors} anchors found | {Stage1} passed href filter ('{LinkPattern}') | {Stage2} passed keyword filter | {Unique} unique URLs returned",
+            provider.Name, allAnchors.Count, stage1Pass, provider.JobLinkContains, stage2Pass, results.Count);
+
         return results;
     }
 }