feat(replay): add ReplayController for /replay/{info,detail}

/replay/info reads from ReplayHistoryReader, newest-first, capped at 50.
/replay/detail returns 400 with result_code=99 - local cache is the
canonical playback source so this endpoint is cache-miss fallback only.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.UnitTests/Controllers/ReplayControllerTests.cs

@@ -0,0 +1,104 @@
+using System.Net;
+using System.Net.Http.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Models;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Replay;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+public class ReplayControllerTests
+{
+    [Test]
+    public async Task ReplayInfo_returns_empty_list_for_fresh_viewer()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(steamId: 76_561_198_000_000_001UL);
+        var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsJsonAsync("/replay/info", new { });
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        var body = await resp.Content.ReadFromJsonAsync<ReplayInfoResponseDto>();
+        Assert.That(body!.ReplayList, Is.Empty);
+    }
+
+    [Test]
+    public async Task ReplayInfo_returns_recent_rows_newest_first()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(steamId: 76_561_198_000_000_001UL);
+
+        using (var seedScope = factory.Services.CreateScope())
+        {
+            var db = seedScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            db.ViewerBattleHistories.AddRange(
+                NewRow(viewerId, battleId: 1, createTime: new DateTime(2026, 6, 1, 0, 0, 0, DateTimeKind.Utc)),
+                NewRow(viewerId, battleId: 2, createTime: new DateTime(2026, 6, 2, 0, 0, 0, DateTimeKind.Utc)),
+                NewRow(viewerId, battleId: 3, createTime: new DateTime(2026, 6, 3, 0, 0, 0, DateTimeKind.Utc)));
+            await db.SaveChangesAsync();
+        }
+
+        var client = factory.CreateAuthenticatedClient(viewerId);
+        var body = await client.PostAsJsonAsync("/replay/info", new { })
+            .ContinueWith(t => t.Result.Content.ReadFromJsonAsync<ReplayInfoResponseDto>())
+            .Unwrap();
+
+        Assert.That(body!.ReplayList.Select(r => r.BattleId).ToList(),
+            Is.EqualTo(new[] { "3", "2", "1" }));
+    }
+
+    [Test]
+    public async Task ReplayInfo_does_not_leak_other_viewers_rows()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerA = await factory.SeedViewerAsync(steamId: 76_561_198_000_000_001UL);
+        long viewerB = await factory.SeedViewerAsync(steamId: 76_561_198_000_000_002UL);
+
+        using (var scope = factory.Services.CreateScope())
+        {
+            var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            db.ViewerBattleHistories.Add(NewRow(viewerA, battleId: 100, createTime: DateTime.UtcNow));
+            db.ViewerBattleHistories.Add(NewRow(viewerB, battleId: 200, createTime: DateTime.UtcNow));
+            await db.SaveChangesAsync();
+        }
+
+        var client = factory.CreateAuthenticatedClient(viewerA);
+        var body = await client.PostAsJsonAsync("/replay/info", new { })
+            .ContinueWith(t => t.Result.Content.ReadFromJsonAsync<ReplayInfoResponseDto>())
+            .Unwrap();
+
+        Assert.That(body!.ReplayList, Has.Count.EqualTo(1));
+        Assert.That(body.ReplayList[0].BattleId, Is.EqualTo("100"));
+    }
+
+    [Test]
+    public async Task ReplayDetail_returns_non_success_status()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(steamId: 76_561_198_000_000_001UL);
+        var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsJsonAsync("/replay/detail", new
+        {
+            viewer_id = viewerId,
+            battle_id = 234_471_983_876L,
+        });
+
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.BadRequest));
+    }
+
+    private static ViewerBattleHistory NewRow(long viewerId, long battleId, DateTime createTime) => new()
+    {
+        ViewerId = viewerId,
+        BattleId = battleId,
+        SelfRotationId = "0",
+        OpponentName = "",
+        OpponentCountryCode = "",
+        OpponentRotationId = "0",
+        BattleStartTime = createTime.AddMinutes(-3),
+        CreateTime = createTime,
+    };
+}