feat(audit): emit USER_DELETED when admin removes a user

Adds actorId param to deleteUser(), captures email before deletion,
emits logAfterCommit(USER_DELETED) with userId+email in payload.
Updates UserController to resolve and pass actorId.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/org/raddatz/familienarchiv/service/UserServiceTest.java

@@ -65,7 +65,7 @@ class UserServiceTest {
         UUID id = UUID.randomUUID();
         when(userRepository.findById(id)).thenReturn(Optional.empty());
 
-        assertThatThrownBy(() -> userService.deleteUser(id))
+        assertThatThrownBy(() -> userService.deleteUser(UUID.randomUUID(), id))
                 .isInstanceOf(DomainException.class);
     }
 
@@ -75,7 +75,7 @@ class UserServiceTest {
         AppUser user = AppUser.builder().id(id).email("gast@example.com").build();
         when(userRepository.findById(id)).thenReturn(Optional.of(user));
 
-        userService.deleteUser(id);
+        userService.deleteUser(UUID.randomUUID(), id);
 
         verify(userRepository).delete(user);
     }
@@ -703,6 +703,28 @@ class UserServiceTest {
         assertThat(result).containsExactly(g);
     }
 
+    // ─── audit: USER_DELETED ──────────────────────────────────────────────────
+
+    @Test
+    void deleteUser_logsUserDeleted_withEmailInPayload() {
+        UUID actorId = UUID.randomUUID();
+        UUID userId = UUID.randomUUID();
+        AppUser user = AppUser.builder().id(userId).email("gone@example.com").build();
+        when(userRepository.findById(userId)).thenReturn(Optional.of(user));
+
+        userService.deleteUser(actorId, userId);
+
+        @SuppressWarnings("unchecked")
+        ArgumentCaptor<java.util.Map<String, Object>> payloadCaptor = ArgumentCaptor.forClass(java.util.Map.class);
+        verify(auditService).logAfterCommit(
+                org.mockito.ArgumentMatchers.eq(AuditKind.USER_DELETED),
+                org.mockito.ArgumentMatchers.eq(actorId),
+                org.mockito.ArgumentMatchers.isNull(),
+                payloadCaptor.capture());
+        assertThat(payloadCaptor.getValue()).containsEntry("email", "gone@example.com");
+        assertThat(payloadCaptor.getValue()).containsKey("userId");
+    }
+
     // ─── audit: USER_CREATED ──────────────────────────────────────────────────
 
     @Test