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>

Jobs/cv-search-job/Tasks/CvSearchJobTask.cs

@@ -14,6 +14,10 @@ using Microsoft.Extensions.Options;
 
 namespace CvSearchJob.Tasks;
 
+/// <summary>
+/// Background job task that processes pending job search sessions: scrapes providers,
+/// scores each URL against the CV via the matcher API, persists results, and sends the results email.
+/// </summary>
 public sealed class CvSearchJobTask : IJobTask
 {
     private readonly IServiceScopeFactory _scopeFactory;
@@ -41,6 +45,11 @@ public sealed class CvSearchJobTask : IJobTask
         _logger = logger;
     }
 
+    /// <summary>
+    /// Called by the scheduler on each tick. Resets orphaned sessions, picks the oldest pending session,
+    /// runs the full search pipeline, and sends the results email.
+    /// Does nothing when <c>JobSearch:Enabled</c> is <c>false</c>.
+    /// </summary>
     public async Task ExecuteAsync(IConfiguration parametersSection, CancellationToken cancellationToken)
     {
         if (!_settings.Enabled) return;
@@ -92,6 +101,10 @@ public sealed class CvSearchJobTask : IJobTask
         }
     }
 
+    /// <summary>
+    /// Runs the full search pipeline for a session: scrapes all providers, deduplicates URLs,
+    /// scores each candidate via the matcher API, and persists results that meet the minimum score threshold.
+    /// </summary>
     private async Task<List<JobSearchResultEntity>> RunSearchAsync(
         JobSearchSessionEntity session,
         CvSearchDbContext db,
@@ -163,6 +176,10 @@ public sealed class CvSearchJobTask : IJobTask
         return results;
     }
 
+    /// <summary>
+    /// Deserialises the provider configuration snapshot stored on the session.
+    /// Falls back to the current live config when the snapshot is absent or unparseable.
+    /// </summary>
     private List<JobProviderConfig> GetProviders(string? providerConfigJson)
     {
         if (string.IsNullOrWhiteSpace(providerConfigJson)) return _settings.Providers.Where(p => p.Enabled).ToList();
@@ -178,6 +195,10 @@ public sealed class CvSearchJobTask : IJobTask
         }
     }
 
+    /// <summary>
+    /// Infers the provider name from the job URL by matching against each provider's <c>JobLinkContains</c> pattern.
+    /// Falls back to the URL hostname when no provider matches.
+    /// </summary>
     private static string GuessProvider(string url, List<JobProviderConfig> providers)
     {
         foreach (var p in providers)
@@ -190,6 +211,9 @@ public sealed class CvSearchJobTask : IJobTask
         return Uri.TryCreate(url, UriKind.Absolute, out var uri) ? uri.Host : "unknown";
     }
 
+    /// <summary>
+    /// Constructs the CV PDF filename from the document ID.
+    /// </summary>
     private static string BuildCvFileName(string cvDocumentId)
     {
         // Strip non-alphanumeric characters so the filename is safe for all OS/email clients.