feat: Phase 3 J/K/L (Sell Decision, Trade Execution, Portfolio Reconciliation) + fix pre-existing build/boot breakage

Completes VS-10/VS-12/VS-14 and makes the solution and Host actually
build and boot for the first time on this branch (main did not build
before this commit).

Root-cause fixes required to reach a green build/boot (not scoped to
J/K/L but blocking any verification of it):
- Restore Polly PackageVersion accidentally deleted from
  Directory.Packages.props (broke KArtSell.Host).
- Remove MediatR dependency from Compliance/VS-04 (package was never
  installed; ICommand/ICommandHandler/IMediator never existed) and
  wire Endpoint -> Handler directly per this repo's convention.
- Migrate FastEndpoints v5 API calls (SendOkAsync/SendAsync/
  SendCreatedAtAsync/SendNotFoundAsync, Description().WithName()) to
  the v7 Send.* fluent API across ~10 endpoint files.
- Fix migrations 0036/0038/0039/0040: rewritten from invalid T-SQL
  (`IF NOT EXISTS ... BEGIN ... END`) to idiomatic Postgres
  (`CREATE TABLE/INDEX IF NOT EXISTS`) — these could not apply to any
  fresh database before this fix.
- Collapse 3 duplicate cross-cutting abstractions that shadowed the
  BuildingBlocks versions and caused type-mismatch compile errors:
  IKrxDataService, IOutboxWriter (ReconcileTradeHandler), IClock
  (ApprovalWorkflow/ApprovalPolicy).
- Inject IClock (BuildingBlocks.Time) in place of direct
  DateTime.Now/UtcNow across 19 files to satisfy the architecture
  test AGENTS.md#DateTime-abstraction rule (13/13 architecture tests
  now pass, was 12/13).
- Register all new and previously-unregistered slices in
  Program.cs DI (SellDecision, TradeExecution, PortfolioReconciliation,
  Compliance, Features/ApprovalWorkflow) — the Host had never
  successfully completed a boot with this code present.
- Disable ("[DontRegister]") the older, route-colliding
  ApprovalWorkflow/ (Workstream H) endpoint set in favor of
  Features/ApprovalWorkflow/ (Workstream G, matches the documented
  Features/<Slice>/ convention); kept for its existing test coverage.
  See TECH_DEBT-017 for the follow-up decision needed.

Verified: dotnet build 0 errors/0 warnings; architecture tests 13/13;
unit tests 54/54 + 18/18; integration tests 34/36 (2 failures are a
local test-DB migration-journal/schema mismatch, not a code defect);
Host boots cleanly and registers all 34 endpoints.

New tech debt recorded: DEBT-017 (duplicate VS-03 implementation),
DEBT-018 (outbox write not co-transactional with entity write in
TradeExecution/PortfolioReconciliation), DEBT-019 (duplicate
BuildingBlocks-shadowing abstractions, partially resolved).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/KArtSell.Host/Program.cs

@@ -175,6 +175,51 @@ builder.Services.AddScoped<KArtSell.Host.Features.Portfolio.IDashboardService>(s
 //         sp.GetRequiredService<KArtSell.Host.Features.SecurityMaster.ISecurityMasterRulesStore>(),
 //         sp.GetRequiredService<IClock>()));
 
+// Shared IDbConnection (per-scope, opened from the pooled data source) for slices using raw Dapper/IDbConnection
+builder.Services.AddScoped<System.Data.IDbConnection>(sp => sp.GetRequiredService<NpgsqlDataSource>().OpenConnection());
+
+// Sell Decision Engine (VS-10)
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.SellDecision.ISellDecisionSql, KArtSell.Modules.ModelOperations.SellDecision.SellDecisionSql>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.SellDecision.IPboValidator, KArtSell.Modules.ModelOperations.SellDecision.PboValidator>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.SellDecision.IDsrValidator, KArtSell.Modules.ModelOperations.SellDecision.DsrValidator>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.SellDecision.IOosValidator, KArtSell.Modules.ModelOperations.SellDecision.OosValidator>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.SellDecision.ISellPriorityRanker, KArtSell.Modules.ModelOperations.SellDecision.SellPriorityRanker>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.SellDecision.IGenerateSellDecisionHandler>(sp =>
+    new KArtSell.Modules.ModelOperations.SellDecision.GenerateSellDecisionHandler(
+        connectionString,
+        sp.GetRequiredService<KArtSell.Modules.ModelOperations.SellDecision.ISellDecisionSql>(),
+        sp.GetRequiredService<KArtSell.Modules.ModelOperations.SellDecision.IPboValidator>(),
+        sp.GetRequiredService<KArtSell.Modules.ModelOperations.SellDecision.IDsrValidator>(),
+        sp.GetRequiredService<KArtSell.Modules.ModelOperations.SellDecision.IOosValidator>(),
+        sp.GetRequiredService<KArtSell.Modules.ModelOperations.SellDecision.ISellPriorityRanker>(),
+        sp.GetRequiredService<IClock>()));
+
+// Trade Execution (VS-12)
+builder.Services.AddHttpClient<KArtSell.Modules.ModelOperations.TradeExecution.IKisTradeExecutionService, KArtSell.Modules.ModelOperations.TradeExecution.KisTradeExecutionService>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.TradeExecution.ITradeSql, KArtSell.Modules.ModelOperations.TradeExecution.TradeSql>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.TradeExecution.SubmitTradeHandler>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.TradeExecution.PollTradeStatusHandler>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.TradeExecution.ConfirmSettlementHandler>();
+
+// Portfolio Reconciliation (VS-14)
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.PortfolioReconciliation.IReconciliationRepository, KArtSell.Modules.ModelOperations.PortfolioReconciliation.ReconciliationSql>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.PortfolioReconciliation.CostBasisCalculator>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.PortfolioReconciliation.MismatchDetector>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.PortfolioReconciliation.ReconciliationEngine>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.PortfolioReconciliation.ReconcileTradeHandler>();
+
+// Approval Workflow (VS-03, maker-checker)
+builder.Services.AddScoped(sp => new KArtSell.Modules.ModelOperations.Features.ApprovalWorkflow.ApprovalWorkflowSql(connectionString));
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Features.ApprovalWorkflow.CreateApprovalProposalHandler>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Features.ApprovalWorkflow.ApproveApprovalHandler>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Features.ApprovalWorkflow.ActivateModelHandler>();
+
+// Compliance / Audit Trail / GDPR (VS-04)
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Compliance.AuditSql>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Compliance.LogAuditEventCommandHandler>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Compliance.ProcessGdprRequestHandler>();
+builder.Services.AddScoped<KArtSell.Modules.ModelOperations.Compliance.GdprRedactionJob>();
+
 builder.Services.AddProblemDetails();
 
 const string authenticationScheme = "KArtSell";