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/JobTokenService.cs

@@ -11,6 +11,9 @@ using Microsoft.Extensions.Options;
 
 namespace Api.Services;
 
+/// <summary>
+/// Creates and validates one-time job search tokens, and creates the corresponding search sessions.
+/// </summary>
 public sealed class JobTokenService : IJobTokenService
 {
     private readonly CvSearchDbContext _db;
@@ -30,6 +33,7 @@ public sealed class JobTokenService : IJobTokenService
         _logger = logger;
     }
 
+    /// <inheritdoc />
     public async Task<string> CreateTokenAsync(string cvDocumentId, string email, string language, CancellationToken ct)
     {
         var token = new JobSearchTokenEntity
@@ -49,6 +53,7 @@ public sealed class JobTokenService : IJobTokenService
         return token.Id;
     }
 
+    /// <inheritdoc />
     public async Task<string> TriggerStartAsync(string tokenId, CancellationToken ct)
     {
         var token = await _db.JobSearchTokens.FirstOrDefaultAsync(x => x.Id == tokenId, ct);
@@ -86,6 +91,10 @@ public sealed class JobTokenService : IJobTokenService
         return StartJobSearchStatus.Started;
     }
 
+    /// <summary>
+    /// Extracts up to 10 meaningful keywords from the CV text using simple heuristics (no LLM).
+    /// Takes the first 5 usable lines, splits them into words, strips punctuation, and deduplicates.
+    /// </summary>
     private static string ExtractKeywords(string cvText)
     {
         var lines = cvText