diff --git a/backend/src/database/migrations/049_add_parent_id_to_kategorien.sql b/backend/src/database/migrations/049_add_parent_id_to_kategorien.sql
new file mode 100644
index 0000000..5d72a20
--- /dev/null
+++ b/backend/src/database/migrations/049_add_parent_id_to_kategorien.sql
@@ -0,0 +1,13 @@
+-- Migration 049: Add parent_id to categories for subcategory support
+-- (048 already created the table without parent_id)
+
+ALTER TABLE ausruestung_kategorien_katalog
+  ADD COLUMN IF NOT EXISTS parent_id INT REFERENCES ausruestung_kategorien_katalog(id) ON DELETE CASCADE;
+
+-- Unique: top-level categories by name
+CREATE UNIQUE INDEX IF NOT EXISTS ausruestung_kat_top_unique
+  ON ausruestung_kategorien_katalog (name) WHERE parent_id IS NULL;
+
+-- Unique: subcategories by (parent_id, name)
+CREATE UNIQUE INDEX IF NOT EXISTS ausruestung_kat_child_unique
+  ON ausruestung_kategorien_katalog (parent_id, name) WHERE parent_id IS NOT NULL;
diff --git a/backend/src/services/ausruestungsanfrage.service.ts b/backend/src/services/ausruestungsanfrage.service.ts
index 9535c50..f8b8315 100644
--- a/backend/src/services/ausruestungsanfrage.service.ts
+++ b/backend/src/services/ausruestungsanfrage.service.ts
@@ -286,8 +286,8 @@ async function getRequests(filters?: { status?: string; anfrager_id?: string })
   const where = conditions.length > 0 ? `WHERE ${conditions.join(' AND ')}` : '';
   const result = await pool.query(
     `SELECT a.*,
-            u.vorname || ' ' || u.nachname AS anfrager_name,
-            u2.vorname || ' ' || u2.nachname AS bearbeitet_von_name,
+            u.display_name AS anfrager_name,
+            u2.display_name AS bearbeitet_von_name,
             (SELECT COUNT(*)::int FROM ausruestung_anfrage_positionen p WHERE p.anfrage_id = a.id) AS positionen_count
      FROM ausruestung_anfragen a
      LEFT JOIN users u  ON u.id  = a.anfrager_id
@@ -314,8 +314,8 @@ async function getMyRequests(userId: string) {
 async function getRequestById(id: number) {
   const reqResult = await pool.query(
     `SELECT a.*,
-            u.vorname || ' ' || u.nachname AS anfrager_name,
-            u2.vorname || ' ' || u2.nachname AS bearbeitet_von_name
+            u.display_name AS anfrager_name,
+            u2.display_name AS bearbeitet_von_name
      FROM ausruestung_anfragen a
      LEFT JOIN users u  ON u.id  = a.anfrager_id
      LEFT JOIN users u2 ON u2.id = a.bearbeitet_von