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/myai-data/Services/DbTemplateService.cs

@@ -6,6 +6,11 @@ using System.Collections.Concurrent;
 
 namespace MyAi.Data.Services;
 
+/// <summary>
+/// Singleton implementation of <see cref="ITemplateService"/> that caches all templates from the
+/// <c>myAi.Templates</c> table and refreshes them every 10 minutes.
+/// Uses <see cref="IServiceScopeFactory"/> to resolve the scoped DbContext from a singleton lifetime.
+/// </summary>
 public sealed class DbTemplateService : ITemplateService
 {
     private readonly IServiceScopeFactory _scopeFactory;
@@ -20,6 +25,7 @@ public sealed class DbTemplateService : ITemplateService
         _logger = logger;
     }
 
+    /// <inheritdoc />
     public string Get(string key, string language = "en")
     {
         EnsureCacheLoaded();
@@ -35,6 +41,7 @@ public sealed class DbTemplateService : ITemplateService
         return key;
     }
 
+    /// <inheritdoc />
     public string Render(string key, string language, params (string Key, string Value)[] placeholders)
     {
         var template = Get(key, language);
@@ -43,6 +50,10 @@ public sealed class DbTemplateService : ITemplateService
         return template;
     }
 
+    /// <summary>
+    /// Reloads all templates from the database when the cache TTL has expired.
+    /// Swaps the cache atomically; logs an error and continues serving the stale cache on failure.
+    /// </summary>
     private void EnsureCacheLoaded()
     {
         if (DateTime.UtcNow - _loadedAt < CacheTtl) return;
@@ -66,5 +77,6 @@ public sealed class DbTemplateService : ITemplateService
         }
     }
 
+    /// <summary>Builds the dictionary key used in the cache.</summary>
     private static string CacheKey(string key, string language) => $"{key}::{language}";
 }

Apis/myai-data/Services/ITemplateService.cs

@@ -1,7 +1,27 @@
 namespace MyAi.Data.Services;
 
+/// <summary>
+/// Provides access to localised string templates stored in the <c>myAi.Templates</c> table.
+/// Implementations are expected to cache templates and refresh periodically.
+/// </summary>
 public interface ITemplateService
 {
+    /// <summary>
+    /// Returns the template value for the given key and language.
+    /// Falls back to <c>"en"</c> when the requested language has no entry.
+    /// Returns the raw key string when no matching template is found.
+    /// </summary>
+    /// <param name="key">Template key (e.g. <c>"html.job-search-start.title"</c>).</param>
+    /// <param name="language">Two-letter language code (e.g. <c>"en"</c>, <c>"ro"</c>).</param>
+    /// <returns>Template value string.</returns>
     string Get(string key, string language = "en");
+
+    /// <summary>
+    /// Retrieves the template and substitutes <c>{{placeholder}}</c> tokens with the provided values.
+    /// </summary>
+    /// <param name="key">Template key.</param>
+    /// <param name="language">Two-letter language code.</param>
+    /// <param name="placeholders">Named replacement pairs in the form <c>("name", value)</c>.</param>
+    /// <returns>Rendered template string with all placeholders replaced.</returns>
     string Render(string key, string language, params (string Key, string Value)[] placeholders);
 }