refactor(db): named tenant query filters (RECOMMENDATIONS #6)

All 11 tenant isolation filters now use EF 10 named filters ("Tenant") so future
filters (soft-delete etc.) can coexist and be selectively ignored per query.
Behaviour unchanged — the existing tenant-isolation tests prove it. 55/55 green.

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

src/InboxIntel.Infrastructure/Persistence/AppDbContext.cs

@@ -47,20 +47,20 @@ public class AppDbContext : DbContext, IAppDbContext
         // its manual `WHERE UserId ==` clause cannot leak across tenants. Applied
         // uniformly to all user-scoped entities so EF sees no filtered/unfiltered
         // navigation mismatch. Bypassed when CurrentUserId is Guid.Empty (workers).
-        modelBuilder.Entity<Email>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<Sender>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<MailThread>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<MailDomain>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<Attachment>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<Label>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<Email>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<Sender>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<MailThread>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<MailDomain>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<Attachment>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<Label>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
         // AUDIT M-6: EmailLabel is the required end of a relationship with the filtered Email
         // entity; without a matching filter EF warns on boot and joins could surface rows whose
         // parent is filtered out. Filter via the Email navigation so the pair is consistent.
-        modelBuilder.Entity<EmailLabel>().HasQueryFilter(el => CurrentUserId == Guid.Empty || el.Email!.UserId == CurrentUserId);
-        modelBuilder.Entity<SyncState>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<AnalyticsAggregate>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<WidgetLayout>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
-        modelBuilder.Entity<UnsubscribeItem>().HasQueryFilter(e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<EmailLabel>().HasQueryFilter("Tenant", el => CurrentUserId == Guid.Empty || el.Email!.UserId == CurrentUserId);
+        modelBuilder.Entity<SyncState>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<AnalyticsAggregate>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<WidgetLayout>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
+        modelBuilder.Entity<UnsubscribeItem>().HasQueryFilter("Tenant", e => CurrentUserId == Guid.Empty || e.UserId == CurrentUserId);
 
         // PostgreSQL full-text search: generated tsvector over subject + body with a
         // GIN index, maintained by the DB and read-only in code. Subject is weighted 'A'