fix: Replace all DateTime.Now/UtcNow with IClock injection (AGENTS.md v16.0)

Resolves architecture test violations:
- Removed all direct DateTime.UtcNow calls
- Injected IClock into 7 service classes
- Added TestClock implementation for tests
- Updated all test constructors with fixture.Clock()
- Fixed MetricsSql comment to avoid false SELECT * detection

Services updated (IClock injection):
- MetricsSql.cs (BuildingBlocks)
- CircuitBreakerPolicyFactory.cs
- KisConnectionPool.cs
- RateLimiterService.cs
- MetricsPolicy.cs
- OpenDartDailyBatchJob.cs
- OpenDartService.cs

Tests updated:
- DatabaseFixture.cs (added Clock() method + TestClock impl)
- CircuitBreakerTests, ObservabilityMetricsTests, OpenDartServiceTests, RateLimiterServiceTests (added fixture.Clock() to constructors)

Result: 95/95 integration tests PASS, DateTime violations 100% resolved

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/KArtSell.Host/Infrastructure/CircuitBreakerPolicy.cs

@@ -1,4 +1,5 @@
 using Dapper;
+using KArtSell.BuildingBlocks.Time;
 using Microsoft.Extensions.Logging;
 using Npgsql;
 using Polly;
@@ -14,6 +15,7 @@ namespace KArtSell.Host.Infrastructure;
 public class CircuitBreakerPolicyFactory
 {
     private readonly NpgsqlDataSource _dataSource;
+    private readonly IClock _clock;
     private readonly ILogger<CircuitBreakerPolicyFactory> _logger;
 
     private static readonly Dictionary<string, IAsyncPolicy<HttpResponseMessage>> Policies = new();
@@ -30,9 +32,10 @@ public class CircuitBreakerPolicyFactory
             new EventId(2, nameof(LogCircuitClosed)),
             "Circuit breaker CLOSED for {ApiName} (recovery successful)");
 
-    public CircuitBreakerPolicyFactory(NpgsqlDataSource dataSource, ILogger<CircuitBreakerPolicyFactory> logger)
+    public CircuitBreakerPolicyFactory(NpgsqlDataSource dataSource, IClock clock, ILogger<CircuitBreakerPolicyFactory> logger)
     {
         _dataSource = dataSource;
+        _clock = clock;
         _logger = logger;
     }
 
@@ -120,10 +123,11 @@ public class CircuitBreakerPolicyFactory
 
         try
         {
+            var now = _clock.UtcNow.UtcDateTime;
             await using var connection = await _dataSource.OpenConnectionAsync();
             await connection.ExecuteAsync(
                 sql,
-                new { apiName, state, reason, now = DateTime.UtcNow },
+                new { apiName, state, reason, now },
                 commandTimeout: 5);
         }
         catch (Exception ex)

src/KArtSell.Host/Infrastructure/KisConnectionPool.cs

@@ -1,4 +1,5 @@
 using Dapper;
+using KArtSell.BuildingBlocks.Time;
 using Microsoft.Extensions.Logging;
 using Npgsql;
 using System.Collections.Concurrent;
@@ -16,6 +17,7 @@ public class KisConnectionPool : IAsyncDisposable
 {
     private readonly NpgsqlDataSource _dataSource;
     private readonly HttpClient _httpClient;
+    private readonly IClock _clock;
     private readonly ILogger<KisConnectionPool> _logger;
 
     private readonly ConcurrentDictionary<Guid, KisConnection> _connections;
@@ -38,10 +40,11 @@ public class KisConnectionPool : IAsyncDisposable
             new EventId(2, nameof(LogTokenRefresh)),
             "KIS token refreshed for connection {ConnectionId}");
 
-    public KisConnectionPool(NpgsqlDataSource dataSource, HttpClient httpClient, ILogger<KisConnectionPool> logger)
+    public KisConnectionPool(NpgsqlDataSource dataSource, HttpClient httpClient, IClock clock, ILogger<KisConnectionPool> logger)
     {
         _dataSource = dataSource;
         _httpClient = httpClient;
+        _clock = clock;
         _logger = logger;
         _connections = new ConcurrentDictionary<Guid, KisConnection>();
         _availableConnections = new PriorityQueue<Guid, int>();
@@ -66,7 +69,7 @@ public class KisConnectionPool : IAsyncDisposable
                     if (_connections.TryGetValue(connId, out var conn))
                     {
                         // Refresh token if needed
-                        if (conn.ExpiresAt < DateTime.UtcNow.AddMinutes(1))
+                        if (conn.ExpiresAt < _clock.UtcNow.UtcDateTime.AddMinutes(1))
                         {
                             await RefreshTokenAsync(conn, cancellationToken);
                         }
@@ -117,14 +120,15 @@ public class KisConnectionPool : IAsyncDisposable
         var connId = Guid.NewGuid();
         var token = await ObtainOAuth2TokenAsync(cancellationToken);
 
+        var now = _clock.UtcNow.UtcDateTime;
         var conn = new KisConnection
         {
             ConnectionId = connId,
             State = "active",
             Priority = KisOperationPriority.Buy,
             TokenHash = HashToken(token),
-            ExpiresAt = DateTime.UtcNow.AddHours(1),
-            CreatedAt = DateTime.UtcNow
+            ExpiresAt = now.AddHours(1),
+            CreatedAt = now
         };
 
         // Persist to database
@@ -138,9 +142,10 @@ public class KisConnectionPool : IAsyncDisposable
     {
         try
         {
+            var now = _clock.UtcNow.UtcDateTime;
             var newToken = await ObtainOAuth2TokenAsync(cancellationToken);
             conn.TokenHash = HashToken(newToken);
-            conn.ExpiresAt = DateTime.UtcNow.AddHours(1);
+            conn.ExpiresAt = now.AddHours(1);
 
             // Log refresh
             const string sql = """
@@ -151,7 +156,7 @@ public class KisConnectionPool : IAsyncDisposable
             await using var connection = await _dataSource.OpenConnectionAsync(cancellationToken);
             await connection.ExecuteAsync(
                 sql,
-                new { connId = conn.ConnectionId, refreshAt = DateTime.UtcNow, tokenHash = conn.TokenHash, now = DateTime.UtcNow },
+                new { connId = conn.ConnectionId, refreshAt = now, tokenHash = conn.TokenHash, now },
                 commandTimeout: 5);
 
             LogTokenRefresh(_logger, conn.ConnectionId, null);
@@ -192,6 +197,7 @@ public class KisConnectionPool : IAsyncDisposable
             VALUES (@connId, @state, @priority, @tokenHash, @expiresAt, @createdAt, @now)
             """;
 
+        var now = _clock.UtcNow.UtcDateTime;
         await using var connection = await _dataSource.OpenConnectionAsync(cancellationToken);
         await connection.ExecuteAsync(
             sql,
@@ -203,7 +209,7 @@ public class KisConnectionPool : IAsyncDisposable
                 tokenHash = conn.TokenHash,
                 expiresAt = conn.ExpiresAt,
                 createdAt = conn.CreatedAt,
-                now = DateTime.UtcNow
+                now
             },
             commandTimeout: 5);
     }

src/KArtSell.Host/Infrastructure/RateLimiterService.cs

@@ -1,4 +1,5 @@
 using Dapper;
+using KArtSell.BuildingBlocks.Time;
 using Microsoft.AspNetCore.Http;
 using Microsoft.Extensions.Logging;
 using Npgsql;
@@ -13,6 +14,7 @@ namespace KArtSell.Host.Infrastructure;
 public class RateLimiterService
 {
     private readonly NpgsqlDataSource _dataSource;
+    private readonly IClock _clock;
     private readonly ILogger<RateLimiterService> _logger;
 
     private static readonly Dictionary<string, RateLimitConfig> ApiConfigs = new()
@@ -34,9 +36,10 @@ public class RateLimiterService
             new EventId(2, nameof(LogQuotaExceeded)),
             "Rate limit: {ApiName} quota exceeded, retry after {RetryAfter}s");
 
-    public RateLimiterService(NpgsqlDataSource dataSource, ILogger<RateLimiterService> logger)
+    public RateLimiterService(NpgsqlDataSource dataSource, IClock clock, ILogger<RateLimiterService> logger)
     {
         _dataSource = dataSource;
+        _clock = clock;
         _logger = logger;
     }
 
@@ -66,7 +69,7 @@ public class RateLimiterService
         await using var connection = await _dataSource.OpenConnectionAsync(cancellationToken);
         var result = await connection.QueryFirstOrDefaultAsync<(int CurrentTokens, int WindowSeconds, int LimitCount)?>(
             sql,
-            new { apiName = apiName.ToLower(), now = DateTime.UtcNow },
+            new { apiName = apiName.ToLower(), now = _clock.UtcNow.UtcDateTime },
             commandTimeout: 5);
 
         if (result == null)
@@ -106,7 +109,7 @@ public class RateLimiterService
         await using var connection = await _dataSource.OpenConnectionAsync(cancellationToken);
         await connection.ExecuteAsync(
             sql,
-            new { apiName = apiName.ToLower(), limit = config.Limit, now = DateTime.UtcNow },
+            new { apiName = apiName.ToLower(), limit = config.Limit, now = _clock.UtcNow.UtcDateTime },
             commandTimeout: 5);
 
         _logger.LogInformation("Rate limit quota reset for {ApiName}: {Limit}/{WindowSeconds}s", apiName, config.Limit, config.WindowSeconds);
@@ -129,7 +132,7 @@ public class RateLimiterService
         {
             await connection.ExecuteAsync(
                 sql,
-                new { apiName, limit = config.Limit, window = config.WindowSeconds, now = DateTime.UtcNow },
+                new { apiName, limit = config.Limit, window = config.WindowSeconds, now = _clock.UtcNow.UtcDateTime },
                 commandTimeout: 5);
         }
 
@@ -148,7 +151,7 @@ public class RateLimiterService
             await using var connection = await _dataSource.OpenConnectionAsync(cancellationToken);
             await connection.ExecuteAsync(
                 sql,
-                new { apiName = apiName.ToLower(), action, now = DateTime.UtcNow },
+                new { apiName = apiName.ToLower(), action, now = _clock.UtcNow.UtcDateTime },
                 commandTimeout: 5);
         }
         catch (Exception ex)