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/GovernanceDbContext.cs

@@ -0,0 +1,27 @@
+using Microsoft.EntityFrameworkCore;
+using TeamUp.Modules.Governance.Domain;
+using TeamUp.SharedKernel.Persistence;
+
+namespace TeamUp.Modules.Governance.Persistence;
+
+internal sealed class GovernanceDbContext(DbContextOptions<GovernanceDbContext> options)
+    : DbContext(options), IModuleDbContext
+{
+    public DbSet<AuditEntry> AuditEntries => Set<AuditEntry>();
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.HasDefaultSchema("governance");
+
+        modelBuilder.Entity<AuditEntry>(entry =>
+        {
+            entry.ToTable("audit_entries");
+            entry.HasKey(a => a.Id);
+            entry.Property(a => a.Action).HasMaxLength(100).IsRequired();
+            entry.Property(a => a.EntityType).HasMaxLength(100).IsRequired();
+            entry.Property(a => a.Details).HasMaxLength(2000);
+            entry.HasIndex(a => a.OccurredAtUtc);
+            entry.HasIndex(a => new { a.EntityType, a.EntityId });
+        });
+    }
+}