Add ProviderParamsFactory and wire inference params

Introduce ProviderParamsFactory to create IProviderInferenceParams based on BackendType. Update Home.razor to set the backend and inference params on the new chat context (casting to IChatConfigurationBuilder) before preserving message history, ensuring the correct provider settings are applied when switching models. Also simplify ChatService by using the null-coalescing assignment (chat.Backend ??= settings.BackendType) to default the backend.

Author: Madzionator

src/MaIN.Domain/Entities/ProviderParams/ProviderParamsFactory.cs

@@ -0,0 +1,19 @@
+using MaIN.Domain.Configuration;
+
+namespace MaIN.Domain.Entities.ProviderParams;
+
+public static class ProviderParamsFactory
+{
+    public static IProviderInferenceParams Create(BackendType backend) => backend switch
+    {
+        BackendType.Self => new LocalInferenceParams(),
+        BackendType.OpenAi => new OpenAiParams(),
+        BackendType.DeepSeek => new DeepSeekParams(),
+        BackendType.GroqCloud => new GroqCloudParams(),
+        BackendType.Xai => new XaiParams(),
+        BackendType.Gemini => new GeminiParams(),
+        BackendType.Anthropic => new AnthropicParams(),
+        BackendType.Ollama => new OllamaParams(),
+        _ => new LocalInferenceParams()
+    };
+}

src/MaIN.InferPage/Components/Pages/Home.razor

@@ -9,6 +9,7 @@
 @using MaIN.Core.Hub.Contexts.Interfaces.ChatContext
 @using MaIN.Domain.Configuration
 @using MaIN.Domain.Entities
+@using MaIN.Domain.Entities.ProviderParams
 @using MaIN.Domain.Exceptions
 @using MaIN.Domain.Models
 @using MaIN.Domain.Models.Abstract
@@ -309,7 +310,12 @@
             if (model != null)
             {
                 var newCtx = AIHub.Chat().WithModel(model, imageGen: Utils.ImageGen);
-                // Preserve history on model switch; cast is safe — ChatContext implements both interfaces.
+                // Set backend and provider params before adding messages.
+                // Cast is safe — ChatContext implements both IChatMessageBuilder and IChatConfigurationBuilder.
+                ((IChatConfigurationBuilder)newCtx)
+                    .WithBackend(Utils.BackendType)
+                    .WithInferenceParams(ProviderParamsFactory.Create(Utils.BackendType));
+                // Preserve history on model switch.
                 ctx = Chat.Messages.Count > 0
                     ? (IChatMessageBuilder)newCtx.WithMessages(Chat.Messages)
                     : newCtx;

src/MaIN.Services/Services/ChatService.cs

@@ -37,7 +37,7 @@ public async Task<ChatResult> Completions(
         {
             chat.ImageGen = true;
         }
-        chat.Backend = chat.Backend ?? settings.BackendType;
+        chat.Backend ??= settings.BackendType;
 
         chat.Messages.Where(x => x.Type == MessageType.NotSet).ToList()
             .ForEach(x => x.Type = chat.Backend != BackendType.Self ? MessageType.CloudLLM : MessageType.LocalLLM);