M1: audit log (Governance) + edit-distance metric

SharedKernel:
- IAuditLog/AuditEvent — append-only audit contract any module writes through.
- EditDistance (Levenshtein + normalized) — the north-star metric, available from day
  one; consumed at edit-and-approve in M5.

Governance module (references SharedKernel only):
- AuditEntry entity; internal GovernanceDbContext (schema "governance") +
  InitialGovernance migration; AuditLog implements IAuditLog.
- GET /api/governance/audit — owner-only (ViewAuditLog), returns recent entries.

Wiring (via the SharedKernel IAuditLog interface — no module references Governance):
- OrgBoard records team.created, task.created, task.moved, task.assigned.
- Identity records invitation.created, member.joined.

Verified: build green; ArchitectureTests 8/8 (Governance references only SharedKernel;
audit flows through the shared interface); IntegrationTests 20/20 — board flow now
asserts task.created/task.moved appear in the audit log, plus EditDistance unit tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Modules/TeamUp.Modules.Governance/Persistence/GovernanceDbContextFactory.cs

@@ -0,0 +1,21 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Design;
+
+namespace TeamUp.Modules.Governance.Persistence;
+
+/// <summary>Design-time factory so `dotnet ef` can build the internal context without a host.</summary>
+internal sealed class GovernanceDbContextFactory : IDesignTimeDbContextFactory<GovernanceDbContext>
+{
+    public GovernanceDbContext CreateDbContext(string[] args)
+    {
+        var connectionString =
+            Environment.GetEnvironmentVariable("ConnectionStrings__Postgres")
+            ?? "Host=localhost;Port=5432;Database=teamup;Username=teamup;Password=teamup";
+
+        var options = new DbContextOptionsBuilder<GovernanceDbContext>()
+            .UseNpgsql(connectionString)
+            .Options;
+
+        return new GovernanceDbContext(options);
+    }
+}