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/Contracts/IRagService.cs

@@ -3,10 +3,46 @@ using Rag.Models.Responses;
 
 namespace Api.Services.Contracts;
 
+/// <summary>
+/// Core RAG (Retrieval-Augmented Generation) operations: document indexing, vector search, and retrieval.
+/// </summary>
 public interface IRagService
 {
+    /// <summary>
+    /// Indexes a plain-text document by classifying it, chunking the text, generating embeddings,
+    /// and persisting the document and its chunks. Returns cached metadata when the text hash already exists.
+    /// </summary>
+    /// <param name="request">Indexing request with text, optional document type, title, and source URL.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>Response with document ID, hash, type, and chunk/character counts.</returns>
     Task<IndexDocumentResponse> IndexTextAsync(IndexDocumentRequest request, CancellationToken ct);
+
+    /// <summary>
+    /// Extracts text from a PDF file, then indexes it the same way as <see cref="IndexTextAsync"/>.
+    /// Returns cached metadata when the extracted text hash already exists.
+    /// </summary>
+    /// <param name="file">Uploaded PDF file (must be ≤ configured max size).</param>
+    /// <param name="documentType">Optional document type hint; if omitted the classifier is used.</param>
+    /// <param name="title">Optional title override; if omitted the title is extracted from the text.</param>
+    /// <param name="sourceUrl">Optional source URL to associate with the document.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>Response with document ID, hash, type, and chunk/character counts.</returns>
     Task<IndexDocumentResponse> IndexPdfAsync(IFormFile file, string? documentType, string? title, string? sourceUrl, CancellationToken ct);
+
+    /// <summary>
+    /// Performs a vector similarity search over indexed document chunks, groups results by document,
+    /// and returns the top-K documents with their best-matching chunks.
+    /// </summary>
+    /// <param name="request">Search request with query text, optional document type filter, and top-K limit.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>Ranked list of matching documents with scored chunk excerpts.</returns>
     Task<SearchResponse> SearchAsync(SearchRequest request, CancellationToken ct);
+
+    /// <summary>
+    /// Retrieves full document details — including the original text — by document ID.
+    /// </summary>
+    /// <param name="documentId">The document's unique identifier.</param>
+    /// <param name="ct">Cancellation token.</param>
+    /// <returns>Document details, or <c>null</c> if no document with that ID exists.</returns>
     Task<RagDocumentDetailsResponse?> GetDocumentAsync(string documentId, CancellationToken ct);
 }