feat: Chat-History auf max. 500 Nachrichten limitieren

Services/DatabaseService.cs

@@ -492,6 +492,28 @@ public class DatabaseService
         );
     }
 
+    public async Task<int> GetActiveMessageCount(string sessionId)
+    {
+        using var conn = CreateConnection();
+        return await conn.ExecuteScalarAsync<int>(@"
+            SELECT COUNT(*) FROM messages m
+            JOIN chains c ON m.chain_id = c.chain_id
+            WHERE c.archive_id IS NULL AND c.session_id = @sessionId",
+            new { sessionId });
+    }
+
+    public async Task<List<MessageRecord>> GetLatestActiveMessages(string sessionId, int limit)
+    {
+        using var conn = CreateConnection();
+        var messages = await conn.QueryAsync<MessageRecord>(@"
+            SELECT m.* FROM messages m
+            JOIN chains c ON m.chain_id = c.chain_id
+            WHERE c.archive_id IS NULL AND c.session_id = @sessionId
+            ORDER BY m.id DESC LIMIT @limit",
+            new { sessionId, limit });
+        return messages.Reverse().ToList();
+    }
+
     public async Task<IEnumerable<MessageRecord>> GetActiveMessagesAfterId(string sessionId, long afterId, int limit = 200)
     {
         using var conn = CreateConnection();