feat: AutoContext-Suche grundlegend verbessern + Embedding-Debug-Tool

Hybrid-Suche (Vektor + FTS5-Keyword), Recency-Boost, Query-Erweiterung
(letzte 2-3 User-Messages), Chunk-Overlapping, FullText-Speicherung,
konfigurierbares Embedding-Modell/MaxSeqLen, deduplizierter AutoContext-
Code (Streaming + CLI shared), Admin-Diagnose-Seite mit Re-Embed-Funktion.
Threshold von 0.45 auf 0.35 gesenkt (Hybrid-Suche ist präziser).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Program.cs

@@ -65,7 +65,14 @@ var chatService = new ChatService(dbService, toolService, memoryService, skillSe
 builder.Services.AddSingleton(chatService);
 
 // Embedding-Services (lokal, ONNX)
-var embeddingService = new Gott.Services.EmbeddingService();
+var embeddingModelDir = serverSettings.Get("EmbeddingModelDir");
+var embeddingMaxSeq = serverSettings.GetInt("EmbeddingMaxSeqLen", 256);
+var embeddingService = new Gott.Services.EmbeddingService(
+    string.IsNullOrEmpty(embeddingModelDir)
+        ? null
+        : Path.Combine(dataDir, "models", embeddingModelDir),
+    embeddingMaxSeq
+);
 builder.Services.AddSingleton(embeddingService);
 var vectorSearchService = new Gott.Services.VectorSearchService(dbPath, embeddingService);
 builder.Services.AddSingleton(vectorSearchService);
@@ -179,6 +186,7 @@ app.MapApiKeysEndpoints();
 app.MapOpenClawEndpoints();
 app.MapRemoteEndpoints();
 app.MapDatabaseExplorerEndpoints();
+app.MapEmbeddingDebugEndpoints();
 app.MapInternalEndpoints();
 
 var port = app.Configuration.GetValue<int>("Port", 19000);