perf(search): trigram indexes for sender/domain filters (#17)

src/InboxIntel.Infrastructure/Persistence/AppDbContext.cs

@@ -75,6 +75,16 @@ public class AppDbContext : DbContext, IAppDbContext
                     "setweight(to_tsvector('english', coalesce(\"BodyText\",'')), 'B')",
                     stored: true);
             modelBuilder.Entity<Email>().HasIndex(e => e.SearchVector).HasMethod("GIN");
+
+            // Trigram GIN indexes so the sender/domain `.Contains()` filters in SearchService
+            // (which translate to `LIKE '%x%'`, non-sargable on a btree) become index-accelerated.
+            // Needs pg_trgm (enabled by the EnablePgTrgm migration).
+            modelBuilder.Entity<Sender>().HasIndex(s => s.Address)
+                .HasMethod("gin").HasOperators("gin_trgm_ops");
+            modelBuilder.Entity<Sender>().HasIndex(s => s.DisplayName)
+                .HasMethod("gin").HasOperators("gin_trgm_ops");
+            modelBuilder.Entity<MailDomain>().HasIndex(d => d.Name)
+                .HasMethod("gin").HasOperators("gin_trgm_ops");
         }
         else
         {