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/Contracts/ICaptchaVerifier.cs

@@ -1,9 +1,21 @@
-using Api.Services.Contracts.Models;
+using Api.Services.Contracts.Models;
 
 namespace Api.Services.Contracts
 {
+    /// <summary>
+    /// Verifies a reCAPTCHA token against the Google verification API.
+    /// </summary>
     public interface ICaptchaVerifier
     {
+        /// <summary>
+        /// Sends the token to the Google reCAPTCHA verification endpoint and
+        /// returns a verdict indicating success, score, and any failure reason.
+        /// </summary>
+        /// <param name="token">The reCAPTCHA token provided by the client.</param>
+        /// <param name="userIp">Optional remote IP address passed to Google for additional risk analysis.</param>
+        /// <param name="expectedAction">Optional action name to validate against the token's embedded action (v3 only).</param>
+        /// <param name="ct">Cancellation token.</param>
+        /// <returns>A <see cref="CaptchaVerdictModel"/> with the verification outcome.</returns>
         Task<CaptchaVerdictModel> VerifyAsync(string token, string? userIp, string? expectedAction, CancellationToken ct);
     }
 }