Improve comments and Swagger annotations across services (#26)

- EmailController: add class summary, full SwaggerResponse/ProducesResponseType
  for 400 and 500, and Description on SwaggerOperation
- ContactController: fix terse "Failed." error message to
  "Could not process subscription."
- FileDownloadController: remove redundant XML <response code> tags from
  the public action doc block; convert private-method /// <summary> to //
  (project convention: no XML doc on internal code)
- CvMatcherService: remove two dead commented-out blocks (old email send
  and BuildEmailBody helper)
- JobTokenService: comment the phone/contact-line regex filter in
  ExtractKeywords
- DocumentClassifier: comment the keyword-frequency scoring approach and
  the confidence formula
- TextChunker: comment the sliding-window step (chunkSize - overlap)
- CvSearchJobTask: comment the GdprConsent = true rationale and the
  BuildCvFileName sanitisation logic
- HtmlJobSearcher: comment GetLeftPart(UriPartial.Path) query-strip dedup

Closes #26

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

Apis/cv-matcher-api/Services/CvMatcherService.cs

@@ -135,13 +135,6 @@ public sealed class CvMatcherService : ICvMatcherService
         result.JobUrl = job.SourceUrl;
         result.Cached = false;
         await _repository.SaveMatchAsync(cv.Id, job.Id, language, result, ct);
-
-        //await _email.SendMatchAsync(
-        //    email,
-        //    $"MyAi.ro CV Match: {result.Score}% - {job.Title}",
-        //    BuildEmailBody(cv, job, result),
-        //    ct);
-
         return result;
     }
 
@@ -188,25 +181,4 @@ public sealed class CvMatcherService : ICvMatcherService
     };
 
     private static string Limit(string value, int max) => value.Length <= max ? value : value[..max];
-
-    //private static string BuildEmailBody(RagDocumentDetails cv, RagDocumentDetails job, JobMatchResponse result) => $"""
-    //    CV Matcher result
-
-    //    CV: {cv.Title}
-    //    Job: {job.Title}
-    //    Job URL: {job.SourceUrl ?? "N/A"}
-    //    Score: {result.Score}%
-
-    //    Summary:
-    //    {result.Summary}
-
-    //    Strengths:
-    //    - {string.Join("\n- ", result.Strengths)}
-
-    //    Gaps:
-    //    - {string.Join("\n- ", result.Gaps)}
-
-    //    Recommendations:
-    //    - {string.Join("\n- ", result.Recommendations)}
-    //    """;
 }