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/rag-api/Services/RagService.cs

@@ -11,6 +11,9 @@ using CommonHelpers;
 
 namespace Api.Services;
 
+/// <summary>
+/// Implements the core RAG pipeline: document classification, chunking, embedding, vector search, and retrieval.
+/// </summary>
 public sealed class RagService : IRagService
 {
     private readonly ITextExtractor _textExtractor;
@@ -36,6 +39,7 @@ public sealed class RagService : IRagService
         _settings = options.Value;
     }
 
+    /// <inheritdoc />
     public async Task<IndexDocumentResponse> IndexTextAsync(IndexDocumentRequest request, CancellationToken ct)
     {
         var text = _textExtractor.Normalize(request.Text ?? string.Empty);
@@ -44,6 +48,7 @@ public sealed class RagService : IRagService
         return await IndexNormalizedTextAsync(text, request.DocumentType, request.Title, request.SourceUrl, request.Metadata, ct);
     }
 
+    /// <inheritdoc />
     public async Task<IndexDocumentResponse> IndexPdfAsync(IFormFile file, string? documentType, string? title, string? sourceUrl, CancellationToken ct)
     {
         if (file.Length <= 0) throw new InvalidOperationException("Uploaded file is empty.");
@@ -57,6 +62,7 @@ public sealed class RagService : IRagService
         return await IndexNormalizedTextAsync(text, documentType, title ?? file.FileName, sourceUrl, new Dictionary<string, string> { ["fileName"] = file.FileName }, ct);
     }
 
+    /// <inheritdoc />
     public async Task<SearchResponse> SearchAsync(SearchRequest request, CancellationToken ct)
     {
         var query = _textExtractor.Normalize(request.QueryText);
@@ -97,6 +103,7 @@ public sealed class RagService : IRagService
         return new SearchResponse { Results = results };
     }
 
+    /// <inheritdoc />
     public async Task<RagDocumentDetailsResponse?> GetDocumentAsync(string documentId, CancellationToken ct)
     {
         var document = await _repository.GetDocumentByIdAsync(documentId, ct);
@@ -112,6 +119,11 @@ public sealed class RagService : IRagService
         };
     }
 
+    /// <summary>
+    /// Core indexing pipeline: computes a text hash for deduplication, classifies and chunks the text,
+    /// generates embeddings for each chunk, and persists the document and chunks to the repository.
+    /// Returns cached metadata without re-indexing when the same text hash and source URL already exist.
+    /// </summary>
     private async Task<IndexDocumentResponse> IndexNormalizedTextAsync(
         string text,
         string? documentType,