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/email-api-data/Services/EmailTemplateService.cs

@@ -5,6 +5,11 @@ using Microsoft.Extensions.Logging;
 
 namespace EmailApi.Data.Services;
 
+/// <summary>
+/// Singleton implementation of <see cref="IEmailTemplateService"/> that caches all email templates
+/// from the database and refreshes them every 10 minutes.
+/// Uses <see cref="IServiceScopeFactory"/> to resolve the scoped repository from a singleton lifetime.
+/// </summary>
 public sealed class EmailTemplateService : IEmailTemplateService
 {
     private readonly IServiceScopeFactory _scopeFactory;
@@ -20,6 +25,7 @@ public sealed class EmailTemplateService : IEmailTemplateService
         _logger = logger;
     }
 
+    /// <inheritdoc />
     public string Get(string key, string language = "en")
     {
         EnsureCacheLoaded();
@@ -35,6 +41,7 @@ public sealed class EmailTemplateService : IEmailTemplateService
         return key;
     }
 
+    /// <inheritdoc />
     public string Render(string key, string language, params (string Key, string Value)[] placeholders)
     {
         var template = Get(key, language);
@@ -43,6 +50,7 @@ public sealed class EmailTemplateService : IEmailTemplateService
         return template;
     }
 
+    /// <inheritdoc />
     public string? GetOperatorCopy(string key, string language)
     {
         EnsureCacheLoaded();
@@ -61,6 +69,10 @@ public sealed class EmailTemplateService : IEmailTemplateService
         return null;
     }
 
+    /// <summary>
+    /// Reloads all templates from the database when the cache TTL has expired.
+    /// Swaps both caches atomically; logs an error and continues serving the stale cache on failure.
+    /// </summary>
     private void EnsureCacheLoaded()
     {
         if (DateTime.UtcNow - _loadedAt < CacheTtl) return;
@@ -91,5 +103,6 @@ public sealed class EmailTemplateService : IEmailTemplateService
         }
     }
 
+    /// <summary>Builds the dictionary key used for both caches.</summary>
     private static string CacheKey(string key, string language) => $"{key}::{language}";
 }