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/cv-matcher-api/Services/Contracts/IJobTextExtractor.cs

@@ -1,6 +1,17 @@
 namespace Api.Services.Contracts;
 
+/// <summary>
+/// Extracts plain text from a job posting, either from a pasted description or by fetching and parsing a URL.
+/// </summary>
 public interface IJobTextExtractor
 {
+    /// <summary>
+    /// Returns normalised plain text for the job posting.
+    /// Prefers <paramref name="jobDescription"/> when provided; otherwise fetches and strips HTML from <paramref name="jobUrl"/>.
+    /// </summary>
+    /// <param name="jobUrl">URL of the job posting page, used when no description is pasted.</param>
+    /// <param name="jobDescription">Pasted job description text; takes priority over URL fetching.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>Normalised plain text, truncated to the configured maximum character limit.</returns>
     Task<string> ExtractAsync(string? jobUrl, string? jobDescription, CancellationToken ct);
 }