feat(warteliste): Nachfrage/Warteliste für Interessenten

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

GerbilManagerWebAPI/ApplicationContext.cs

@@ -25,6 +25,7 @@ public class ApplicationContext : DbContext
     public DbSet<Request> Requests => Set<Request>();
     public DbSet<MailSettings> MailSettings => Set<MailSettings>();
     public DbSet<Feedback> Feedback => Set<Feedback>();
+    public DbSet<WaitingListEntry> WaitingListEntries => Set<WaitingListEntry>();
 
     // Keep Gerbil.NameSearch in sync on every save (separator-insensitive search key),
     // so it can never drift from Name regardless of which code path mutates the entity.
@@ -212,6 +213,15 @@ public class ApplicationContext : DbContext
             e.HasIndex(f => f.CreatedAt);
         });
 
+        // WAITLIST: same relationship-free pattern as Feedback. ContactId is a plain
+        // nullable Guid column (no navigation property → EF creates NO foreign key), so
+        // the import re-ingest wipe of Contacts never cascades into — or breaks —
+        // waiting-list rows. They survive re-ingest, which is the whole point.
+        modelBuilder.Entity<WaitingListEntry>(e =>
+        {
+            e.HasIndex(w => w.CreatedAt);
+        });
+
         // DB-4: German collation on remaining searched/sorted text columns (Npgsql-only).
         if (isNpgsql)
         {