Add XML doc to all service interfaces and implementations (#26)

- Update CLAUDE.md: replace incorrect 'no XML doc on internal code' rule
  with the correct convention (XML doc on all public methods and
  non-trivial private/protected helpers)
- Restore /// <summary> on FileDownloadController private helpers
  (HandleRangeRequest, StreamRangeAsync)
- Add full XML doc to all service contracts:
  ICaptchaVerifier, IEmailSender, ICvMatcherService, IJobTextExtractor,
  IJobTokenService, IDocumentClassifier, IRagService, ITextChunker,
  ITextExtractor, IEmailTemplateService, ITemplateService
- Add /// <summary> and /// <inheritdoc /> to all concrete service classes
  and their methods: RecaptchaVerifier, EmailApiEmailSender,
  SmtpEmailDispatcher, CvMatcherService, JobTextExtractor, JobTokenService,
  RagService, DocumentClassifier, TextChunker, TextExtractor,
  HtmlJobSearcher, CvSearchEmailSender, CvSearchJobTask,
  EmailTemplateService, DbTemplateService

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

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

@@ -7,6 +7,10 @@ using Microsoft.Extensions.Logging;
 
 namespace CvSearchJob.Services;
 
+/// <summary>
+/// Sends job search results emails to the session user and the operator copy address,
+/// with an optional CV PDF attachment.
+/// </summary>
 public sealed class CvSearchEmailSender
 {
     private readonly IEmailApiClient _emailApi;
@@ -23,6 +27,16 @@ public sealed class CvSearchEmailSender
         _logger = logger;
     }
 
+    /// <summary>
+    /// Builds and sends the job search results email.
+    /// Resolves the recipient list from <paramref name="toEmail"/> and the operator copy address
+    /// stored in the email template. Does nothing when no recipients can be resolved.
+    /// </summary>
+    /// <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="language">Two-letter language code for template rendering.</param>
+    /// <param name="ct">Cancellation token.</param>
     public async Task SendResultsAsync(
         string toEmail,
         string? attachmentFileName,
@@ -64,6 +78,10 @@ public sealed class CvSearchEmailSender
         }
     }
 
+    /// <summary>
+    /// Renders the HTML email body from the results list.
+    /// Returns the empty-results template when no results are present.
+    /// </summary>
     private string BuildBody(IReadOnlyList<JobSearchResultEntity> results, string language)
     {
         if (results.Count == 0)
@@ -92,6 +110,10 @@ public sealed class CvSearchEmailSender
             ("items", items.ToString()));
     }
 
+    /// <summary>
+    /// Attempts to deserialise the stored result JSON into a <see cref="JobMatchResponse"/>.
+    /// Returns <c>null</c> on parse failure so the email still renders without a summary.
+    /// </summary>
     private static JobMatchResponse? TryParseResult(string json)
     {
         try