Implement LLM provider configuration and update user settings

- Added functionality to update the default LLM provider for users via a new endpoint in UserController.
- Introduced LlmProvider enum to manage available LLM options: Auto, Gemini, OpenAI, and Claude.
- Updated User and UserEntity models to include DefaultLlmProvider property.
- Enhanced database context and migrations to support the new LLM provider configuration.
- Integrated LLM services into the application bootstrap for dependency injection.
- Updated TypeScript API client to include methods for managing LLM providers and chat requests.

src/Managing.Infrastructure.Database/Migrations/ManagingDbContextModelSnapshot.cs

@@ -1441,6 +1441,11 @@ namespace Managing.Infrastructure.Databases.Migrations
                     b.Property<string>("DefaultExchange")
                         .HasColumnType("text");
 
+                    b.Property<string>("DefaultLlmProvider")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("text")
+                        .HasDefaultValueSql("'Auto'");
+
                     b.Property<bool>("EnableAutoswap")
                         .HasColumnType("boolean");