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.Modules.ModelOperations/ApprovalWorkflow/ApprovalSql.cs

@@ -7,15 +7,18 @@ using System.Linq;
 using System.Text.Json;
 using System.Threading.Tasks;
 using Dapper;
+using KArtSell.BuildingBlocks.Time;
 using Npgsql;
 
 public class ApprovalSql
 {
     private readonly string _connectionString;
+    private readonly IClock _clock;
 
-    public ApprovalSql(string connectionString)
+    public ApprovalSql(string connectionString, IClock clock)
     {
         _connectionString = connectionString;
+        _clock = clock;
     }
 
     public async Task<ApprovalProposal?> GetProposalByIdAsync(Guid id, DateTimeOffset cutoff)
@@ -75,7 +78,7 @@ public class ApprovalSql
             modelId,
             status,
             createdBy,
-            createdAt = DateTimeOffset.UtcNow,
+            createdAt = _clock.UtcNow,
             justification,
             effectiveAt,
             publishedAt,
@@ -102,7 +105,7 @@ public class ApprovalSql
             id,
             newStatus,
             approvedBy,
-            approvedAt = DateTimeOffset.UtcNow,
+            approvedAt = _clock.UtcNow,
             approvalNotes,
             publishedAt
         });
@@ -124,7 +127,7 @@ public class ApprovalSql
             evidenceType,
             evidenceUrl,
             comment,
-            publishedAt = DateTimeOffset.UtcNow,
+            publishedAt = _clock.UtcNow,
             correlationId
         });
     }
@@ -146,9 +149,9 @@ public class ApprovalSql
             proposalId,
             eventType,
             actorEmail,
-            eventAt = DateTimeOffset.UtcNow,
+            eventAt = _clock.UtcNow,
             details = detailsJson,
-            publishedAt = DateTimeOffset.UtcNow,
+            publishedAt = _clock.UtcNow,
             correlationId
         });
     }
@@ -191,7 +194,7 @@ public class ApprovalSql
         };
     }
 
-    private class ApprovalProposalRaw
+    private sealed class ApprovalProposalRaw
     {
         public Guid Id { get; set; }
         public Guid ModelId { get; set; }