fix: Resolve backend build errors - add RootNamespace, OutputType, GlobalUsings, and code analysis settings

src/KArtSell.Modules.SignalEngine/Features/EvaluateResearchSellPolicy/Endpoint.cs

@@ -9,7 +9,7 @@ public sealed class Endpoint(SellPolicyChain policyChain) : Endpoint<Request, Re
     {
         Post("/internal/v1/research/sell-policy/evaluate");
         Roles("Quant", "System");
-        Description(x => x.WithTags("ResearchOnly"));
+        Tags("ResearchOnly");
     }
 
     public override async Task HandleAsync(Request req, CancellationToken ct)

src/KArtSell.Modules.SignalEngine/Features/GenerateSellDecision/Endpoint.cs

@@ -1,4 +1,6 @@
 using FastEndpoints;
+using Microsoft.AspNetCore.Http;
+using System.Text.Json;
 using KArtSell.Modules.SignalEngine.Application;
 
 namespace KArtSell.Modules.SignalEngine.Features.GenerateSellDecision;