Add github_code_search tool + scanned key type field

- New tool: github_code_search (GitHub Code Search API with text-match fragments)
- Tool available when GitHubToken is configured in server settings
- Registered in AnthropicService + ChatService tool pipelines
- ToolService: SetHttpClientFactory() pattern for lazy DI resolution
- ScannedKeyRecord: type field (anthropic_oauth, anthropic_api, anthropic_unknown, unknown)
- DetectKeyType() based on key prefix
- DB migration: type column with default 'anthropic_oauth'
- Frontend: type label in scanned keys list

wwwroot/js/pages/api-keys-page.js

@@ -362,6 +362,8 @@ registerPage('api-keys', {
         var metaParts = [];
         var sourceIcons = { github: '🐙 GitHub', serper: '🔍 Google', gist: '📋 Gist', pastebin: '📄 Pastebin' };
         metaParts.push(sourceIcons[sk.source] || sk.source || 'github');
+        var typeLabels = { anthropic_oauth: 'OAuth', anthropic_api: 'API', anthropic_unknown: 'Anthropic', unknown: '?' };
+        metaParts.push(typeLabels[sk.type] || sk.type || '?');
         metaParts.push(formatKeyStatus(sk.status));
         if (sk.plan && sk.plan !== 'Unknown') metaParts.push(sk.plan);
         if (sk.checkedAt) metaParts.push(new Date(sk.checkedAt).toLocaleString());