feat(email): add durable send ledger

Tracks only idempotency and delivery metadata; recipient, subject, and body are excluded. No provider send path is enabled.

JobTrackerApi/Program.cs

@@ -45,6 +45,7 @@ builder.Services.AddScoped<ICurrentUserService>(sp => sp.GetRequiredService<Curr
 builder.Services.AddSingleton<BackgroundTenantRunner>();
 builder.Services.AddSingleton(TimeProvider.System);
 builder.Services.AddScoped<UserOperationStore>();
+builder.Services.AddScoped<EmailSendAttemptStore>();
 builder.Services.AddScoped<AiOperationAdmission>();
 builder.Services.AddScoped<StrategySnapshotService>();
 builder.Services.AddSingleton<IAiOperationHandler, StrategySnapshotOperationHandler>();