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>

Apis/api/Services/RecaptchaVerifier.cs

@@ -5,6 +5,9 @@ using Models.Settings;
 
 namespace Api.Services
 {
+    /// <summary>
+    /// Verifies reCAPTCHA v2/v3 tokens by calling the Google site-verify API.
+    /// </summary>
     public sealed class RecaptchaVerifier : ICaptchaVerifier
     {
         private readonly HttpClient _http;
@@ -18,6 +21,7 @@ namespace Api.Services
             _log = log;
         }
 
+        /// <inheritdoc />
         public async Task<CaptchaVerdictModel> VerifyAsync(string token, string? userIp, string? expectedAction, CancellationToken ct)
         {
             _log.LogDebug("Verifying captcha token for IP {Ip}", userIp ?? "unknown");