feat(guild): add Guild aggregate schema + migration

SVSim.UnitTests/Persistence/GuildSchemaTests.cs

@@ -0,0 +1,60 @@
+using NUnit.Framework;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using SVSim.Database;
+using SVSim.Database.Entities.Guild;
+
+namespace SVSim.UnitTests.Persistence;
+
+[TestFixture]
+public class GuildSchemaTests
+{
+    private SVSimDbContext NewCtx() =>
+        new(NullLogger<SVSimDbContext>.Instance,
+            new DbContextOptionsBuilder<SVSimDbContext>()
+            .UseInMemoryDatabase($"guild-schema-{System.Guid.NewGuid()}")
+            .Options);
+
+    [Test]
+    public async Task Can_insert_guild_and_member_round_trip()
+    {
+        await using var db = NewCtx();
+        var g = new Guild
+        {
+            GuildId = 100_000_001, Name = "Alpha", Description = "",
+            LeaderViewerId = 42, EmblemId = 100000000,
+            Activity = GuildActivity.All, JoinCondition = GuildJoinCondition.Free,
+            CreatedAt = new System.DateTime(2026, 1, 1, 0, 0, 0, System.DateTimeKind.Utc),
+        };
+        g.Members.Add(new GuildMember
+        {
+            ViewerId = 42, Role = GuildRole.Leader,
+            JoinedAt = g.CreatedAt,
+        });
+        db.Guilds.Add(g);
+        await db.SaveChangesAsync();
+
+        var loaded = await db.Guilds.Include(x => x.Members).SingleAsync();
+        Assert.That(loaded.GuildId, Is.EqualTo(100_000_001));
+        Assert.That(loaded.Members, Has.Count.EqualTo(1));
+        Assert.That(loaded.Members[0].Role, Is.EqualTo(GuildRole.Leader));
+    }
+
+    [Test]
+    public async Task GuildMember_ViewerId_uniqueness_is_enforced()
+    {
+        await using var db = NewCtx();
+        db.Guilds.Add(new Guild { GuildId = 1, Name = "G1", Activity = GuildActivity.All, JoinCondition = GuildJoinCondition.Free, CreatedAt = System.DateTime.UtcNow,
+            Members = { new GuildMember { ViewerId = 7, Role = GuildRole.Leader, JoinedAt = System.DateTime.UtcNow } } });
+        db.Guilds.Add(new Guild { GuildId = 2, Name = "G2", Activity = GuildActivity.All, JoinCondition = GuildJoinCondition.Free, CreatedAt = System.DateTime.UtcNow,
+            Members = { new GuildMember { ViewerId = 7, Role = GuildRole.Leader, JoinedAt = System.DateTime.UtcNow } } });
+
+        // InMemory provider does NOT enforce unique indexes — this test asserts the model is configured;
+        // we verify enforcement under Postgres in an integration test in Task 3.
+        var idx = db.Model.FindEntityType(typeof(GuildMember))!
+            .GetIndexes().Single(i => i.Properties.Single().Name == nameof(GuildMember.ViewerId));
+        Assert.That(idx.IsUnique, Is.True);
+
+        await Task.Yield();
+    }
+}