feat: Serper Web Search als Agent-Tool

- ToolService: serper_web_search Tool-Definition + ExecuteSerperWebSearch()
  Google-Suche via Serper.dev API mit Titel, Link, Snippet
  Knowledge Graph + Answer Box + organische Ergebnisse
- AgentRecord: UseSerperSearch Property (Default: false)
- DB-Migration: use_serper_search Spalte
- AnthropicService + ChatService: useSerperSearch Parameter durchreichen
- ChatEndpoint + AgentEndpoint: useSerperSearch in API
- Frontend: Checkbox, Badge (Serper Search), laden/speichern
- Aktivierung: Agent-Checkbox + SerperApiKey in Server-Einstellungen

Services/ToolService.cs

@@ -33,6 +33,7 @@ public class ToolService
 
     private int ExecuteTimeoutSeconds => _config.GetValue<int>("ExecuteTimeout", 180);
     public bool HasGitHubToken => !string.IsNullOrWhiteSpace(_config["GitHubToken"]);
+    public bool HasSerperKey => !string.IsNullOrWhiteSpace(_config["SerperApiKey"]);
     public const string AskUserChoiceToolName = "ask_user_choice";
 
     /// <summary>
@@ -43,7 +44,7 @@ public class ToolService
     {
         "read_file", "list_files", "glob", "grep", "execute", "todo_write",
         "memory_read", "memory_write", "memory_list", "memory_search",
-        "remote_execute", "github_code_search", AskUserChoiceToolName
+        "remote_execute", "github_code_search", "serper_web_search", AskUserChoiceToolName
     };
 
     public object[] FilterReadOnlyTools(object[] tools)
@@ -63,7 +64,7 @@ public class ToolService
         return filtered.ToArray();
     }
 
-    public object[] GetToolDefinitions(bool includeFileTools = false, bool includeMemory = false, bool includeUserChoice = true, bool includeRemote = false, bool includeMemorySearch = false, bool includeSendToSession = false, bool includeGitHubSearch = false)
+    public object[] GetToolDefinitions(bool includeFileTools = false, bool includeMemory = false, bool includeUserChoice = true, bool includeRemote = false, bool includeMemorySearch = false, bool includeSendToSession = false, bool includeGitHubSearch = false, bool includeSerperSearch = false)
     {
         var allTools = new List<object>();
         if (includeUserChoice)
@@ -80,6 +81,8 @@ public class ToolService
             allTools.Add(GetSendToSessionTool());
         if (includeGitHubSearch)
             allTools.Add(GetGitHubCodeSearchTool());
+        if (includeSerperSearch)
+            allTools.Add(GetSerperWebSearchTool());
         return allTools.ToArray();
     }
 
@@ -814,6 +817,10 @@ public class ToolService
             {
                 return await ExecuteGitHubCodeSearch(input, cancellationToken);
             }
+            case "serper_web_search":
+            {
+                return await ExecuteSerperWebSearch(input, cancellationToken);
+            }
             default:
                 return $"Fehler: Unbekanntes Tool: {name}";
         }
@@ -929,4 +936,120 @@ public class ToolService
             return $"GitHub-Suche fehlgeschlagen: {ex.Message}";
         }
     }
+
+    // ── Serper Web Search ──
+
+    private object GetSerperWebSearchTool()
+    {
+        return new
+        {
+            name = "serper_web_search",
+            description = "Durchsucht das Internet via Google (Serper.dev API). Gibt strukturierte Suchergebnisse zurück mit Titel, Link und Snippet. Unterstützt alle Google-Suchoperatoren (z.B. exakte Phrasen mit Anführungszeichen, site:, filetype:). Nutze dies für Webrecherche, aktuelle Informationen oder das Finden spezifischer Inhalte im Internet.",
+            input_schema = new
+            {
+                type = "object",
+                properties = new Dictionary<string, object>
+                {
+                    ["query"] = new { type = "string", description = "Suchbegriff (unterstützt Google-Suchsyntax, z.B. '\"exakte Phrase\"', 'site:github.com', 'filetype:pdf')" },
+                    ["num"] = new { type = "integer", description = "Anzahl Ergebnisse (1-100, Default: 10)" }
+                },
+                required = new[] { "query" }
+            }
+        };
+    }
+
+    private async Task<string> ExecuteSerperWebSearch(JsonElement input, CancellationToken ct)
+    {
+        var apiKey = _config["SerperApiKey"] ?? "";
+        if (string.IsNullOrWhiteSpace(apiKey))
+            return "Fehler: Kein SerperApiKey konfiguriert. Bitte in den Server-Einstellungen hinterlegen.";
+
+        var query = input.GetProperty("query").GetString() ?? "";
+        if (string.IsNullOrWhiteSpace(query))
+            return "Fehler: Suchbegriff (query) darf nicht leer sein.";
+
+        var num = input.TryGetProperty("num", out var numProp) ? Math.Clamp(numProp.GetInt32(), 1, 100) : 10;
+
+        try
+        {
+            var client = _httpFactory.CreateClient();
+            client.DefaultRequestHeaders.Add("X-API-KEY", apiKey);
+
+            var requestBody = JsonSerializer.Serialize(new { q = query, num = num });
+            var content = new StringContent(requestBody, Encoding.UTF8, "application/json");
+
+            var response = await client.PostAsync("https://google.serper.dev/search", content, ct);
+
+            if (!response.IsSuccessStatusCode)
+            {
+                var errorBody = await response.Content.ReadAsStringAsync(ct);
+                return $"Serper API Fehler {(int)response.StatusCode}: {errorBody}";
+            }
+
+            var json = await response.Content.ReadAsStringAsync(ct);
+            var doc = JsonDocument.Parse(json);
+            var root = doc.RootElement;
+
+            var sb = new StringBuilder();
+
+            // Knowledge Graph (wenn vorhanden)
+            if (root.TryGetProperty("knowledgeGraph", out var kg))
+            {
+                if (kg.TryGetProperty("title", out var kgTitle))
+                    sb.AppendLine($"## {kgTitle.GetString()}");
+                if (kg.TryGetProperty("description", out var kgDesc))
+                    sb.AppendLine(kgDesc.GetString());
+                sb.AppendLine();
+            }
+
+            // Answer Box (wenn vorhanden)
+            if (root.TryGetProperty("answerBox", out var ab))
+            {
+                sb.AppendLine("### Direkte Antwort");
+                if (ab.TryGetProperty("title", out var abTitle))
+                    sb.AppendLine($"**{abTitle.GetString()}**");
+                if (ab.TryGetProperty("answer", out var abAnswer))
+                    sb.AppendLine(abAnswer.GetString());
+                else if (ab.TryGetProperty("snippet", out var abSnippet))
+                    sb.AppendLine(abSnippet.GetString());
+                sb.AppendLine();
+            }
+
+            // Organische Ergebnisse
+            if (root.TryGetProperty("organic", out var organic))
+            {
+                var results = organic.EnumerateArray().ToArray();
+                sb.AppendLine($"**{results.Length} Ergebnisse:**");
+                sb.AppendLine();
+
+                var index = 0;
+                foreach (var item in results)
+                {
+                    index++;
+                    var title = item.TryGetProperty("title", out var t) ? t.GetString() : "";
+                    var link = item.TryGetProperty("link", out var l) ? l.GetString() : "";
+                    var snippet = item.TryGetProperty("snippet", out var s) ? s.GetString() : "";
+
+                    sb.AppendLine($"### {index}. {title}");
+                    sb.AppendLine($"🔗 {link}");
+                    if (!string.IsNullOrEmpty(snippet))
+                        sb.AppendLine(snippet);
+                    sb.AppendLine();
+                }
+            }
+
+            if (sb.Length == 0)
+                sb.AppendLine("Keine Ergebnisse gefunden.");
+
+            return sb.ToString();
+        }
+        catch (TaskCanceledException)
+        {
+            return "Serper-Suche abgebrochen (Timeout).";
+        }
+        catch (Exception ex)
+        {
+            return $"Serper-Suche fehlgeschlagen: {ex.Message}";
+        }
+    }
 }