fix(event-types): harden setup window + catalog validation (codex review)

Three review rounds on PR #801; fixes in response:

- isValidEventType: live catalog is authoritative when it has rows — a
  deleted or deactivated slug no longer validates via the legacy
  fallback (fallback now only serves an empty-catalog install)
- deleteEventType: refuse deleting the last (and last ACTIVE) type;
  updateEventType: refuse deactivating the last active type (unknown
  slugs are rejected since the validator change, so an empty active
  catalog would brick event creation)
- setup window fails closed: only an explicit stored `false` opens it
  (a portable-backup restore can leave the key absent) and a normal
  admin login durably closes it (abandoned-wizard case)
- reserved bootstrap keys (setup_wizard_completed, setup_token) are
  stripped from ALL generic settings upserts (/general, /security,
  /analytics, /seo) so the marker is genuinely one-way
- wizard step: deletes ordered so the catalog can never end up empty,
  and a genuinely failed system-type deletion reloads the list and
  stays on the step instead of advancing past the only window in which
  it can be retried
- CreateEventPage: snap the hardcoded initial 'wedding' selection to
  the first active type when the catalog no longer contains it
- v1 API: new GET /event-types (read scope) so token clients can
  discover valid slugs; OpenAPI enum replaced with the live-catalog
  description

frontend/src/components/admin/SetupEventTypesStep.tsx

@@ -66,9 +66,16 @@ export const SetupEventTypesStep: React.FC<Props> = ({ onDone }) => {
     setRows((prev) => (prev ? [...prev, { name: '', slug_prefix: '', emoji: '📷' }] : prev));
   };
 
-  // Apply the diff (delete → update → create), then advance. Best-effort like
-  // the other wizard steps — a partial failure warns but never traps the user;
-  // everything here is editable later in Settings → Event Types.
+  // Apply the diff, then advance. Ordering matters twice over: deletes first
+  // frees a default's slug for a rename/re-create ("replace Wedding with my
+  // own 'wedding'"), but deleting everything BEFORE a replacement exists could
+  // empty the catalog if the creation then fails. So: when at least one
+  // existing row is kept the catalog can never go empty → delete first; when
+  // the user replaces ALL types → create first and only delete once at least
+  // one replacement actually persisted. (The backend additionally refuses
+  // deleting the last remaining type.) Best-effort like the other wizard
+  // steps — a partial failure warns but never traps the user; everything here
+  // is editable later in Settings → Event Types.
   const handleContinue = async () => {
     if (!rows) return;
     const kept = rows.filter((r) => r.name.trim() && r.slug_prefix.trim());
@@ -78,34 +85,74 @@ export const SetupEventTypesStep: React.FC<Props> = ({ onDone }) => {
     }
     setSaving(true);
     let failures = 0;
-    for (const id of deletedIds) {
-      try {
-        await eventTypesService.deleteEventType(id);
-      } catch {
-        failures += 1;
-      }
-    }
-    for (const row of kept) {
-      try {
-        if (row.id !== undefined) {
-          const before = original.get(row.id);
-          const updates: { name?: string; slug_prefix?: string } = {};
-          if (before && row.name.trim() !== before.name) updates.name = row.name.trim();
-          if (before && row.slug_prefix !== before.slug_prefix) updates.slug_prefix = row.slug_prefix;
-          if (Object.keys(updates).length > 0) {
-            await eventTypesService.updateEventType(row.id, updates);
-          }
-        } else {
-          await eventTypesService.createEventType({
-            name: row.name.trim(),
-            slug_prefix: row.slug_prefix,
-            emoji: row.emoji,
-          });
+    let deleteFailures = 0;
+    let createdOk = 0;
+
+    const applyDeletes = async () => {
+      for (const id of deletedIds) {
+        try {
+          await eventTypesService.deleteEventType(id);
+        } catch {
+          deleteFailures += 1;
         }
-      } catch {
-        failures += 1;
       }
+    };
+    const applyCreatesAndUpdates = async () => {
+      for (const row of kept) {
+        try {
+          if (row.id !== undefined) {
+            const before = original.get(row.id);
+            const updates: { name?: string; slug_prefix?: string } = {};
+            if (before && row.name.trim() !== before.name) updates.name = row.name.trim();
+            if (before && row.slug_prefix !== before.slug_prefix) updates.slug_prefix = row.slug_prefix;
+            if (Object.keys(updates).length > 0) {
+              await eventTypesService.updateEventType(row.id, updates);
+            }
+          } else {
+            await eventTypesService.createEventType({
+              name: row.name.trim(),
+              slug_prefix: row.slug_prefix,
+              emoji: row.emoji,
+            });
+            createdOk += 1;
+          }
+        } catch {
+          failures += 1;
+        }
+      }
+    };
+
+    const keptExisting = kept.filter((r) => r.id !== undefined).length;
+    if (keptExisting > 0) {
+      await applyDeletes();
+      await applyCreatesAndUpdates();
+    } else {
+      await applyCreatesAndUpdates();
+      if (deletedIds.length > 0 && createdOk === 0) {
+        // Every replacement failed — deleting now would empty the catalog.
+        // Keep the seeded types and stay on the step.
+        setSaving(false);
+        toast.error(t('setup.eventTypes.atLeastOne'));
+        return;
+      }
+      await applyDeletes();
     }
+
+    // A failed DELETE must not slip past this step: system types are only
+    // deletable inside this window, so once the wizard finishes the request
+    // can never be retried. Reload the live catalog and stay for a retry.
+    if (deleteFailures > 0) {
+      try {
+        const types = await eventTypesService.getEventTypes();
+        setOriginal(new Map(types.map((et) => [et.id, et])));
+        setRows(types.map((et) => ({ id: et.id, name: et.name, slug_prefix: et.slug_prefix, emoji: et.emoji })));
+      } catch { /* keep the local rows if the reload fails */ }
+      setDeletedIds([]);
+      setSaving(false);
+      toast.error(t('setup.eventTypes.deleteFailed'));
+      return;
+    }
+
     setSaving(false);
     if (failures > 0) toast.warn(t('setup.eventTypes.saveFailed'));
     onDone();

frontend/src/i18n/locales/de.json

@@ -3622,7 +3622,8 @@
       "hint": "Das URL-Präfix erscheint in Galerie-Links (z.B. familie-mueller-2025-06-01). Symbole, Themes und Reihenfolge können Sie später unter Einstellungen → Veranstaltungsarten anpassen.",
       "atLeastOne": "Behalten Sie mindestens eine Veranstaltungsart — jede Galerie braucht eine.",
       "loadFailed": "Veranstaltungsarten konnten nicht geladen werden — Sie können sie später unter Einstellungen → Veranstaltungsarten anpassen.",
-      "saveFailed": "Einige Änderungen konnten nicht gespeichert werden — Sie können sie unter Einstellungen → Veranstaltungsarten abschließen."
+      "saveFailed": "Einige Änderungen konnten nicht gespeichert werden — Sie können sie unter Einstellungen → Veranstaltungsarten abschließen.",
+      "deleteFailed": "Eine Löschung ist fehlgeschlagen — die Liste wurde neu geladen. Mitgelieferte Arten können nur hier gelöscht werden; versuchen Sie es erneut oder fahren Sie mit ihnen fort."
     },
     "community": {
       "subtitle": "Alles bereit",

frontend/src/i18n/locales/en.json

@@ -3511,7 +3511,8 @@
       "hint": "The URL prefix appears in gallery links (e.g. family-smith-2025-06-01). Icons, themes and order can be tuned later in Settings → Event Types.",
       "atLeastOne": "Keep at least one event type — every gallery needs one.",
       "loadFailed": "Could not load the event types — you can adjust them later in Settings → Event Types.",
-      "saveFailed": "Some event type changes could not be saved — you can finish them in Settings → Event Types."
+      "saveFailed": "Some event type changes could not be saved — you can finish them in Settings → Event Types.",
+      "deleteFailed": "A deletion failed — the list has been reloaded. Built-in types can only be deleted here, so retry or continue with them kept."
     },
     "community": {
       "subtitle": "You're all set",

frontend/src/pages/admin/CreateEventPage.tsx

@@ -182,6 +182,18 @@ export const CreateEventPage: React.FC = () => {
     [eventTypes]
   );
 
+  // The hardcoded initial form value ('wedding') may not exist in the live
+  // catalog — the setup wizard can rename or delete the defaults (#800), and
+  // the backend now rejects unknown slugs. Snap to the first active type; a
+  // user-picked value is always in the list, so this never fights the user.
+  useEffect(() => {
+    if (!availableEventTypes.length) return;
+    if (!availableEventTypes.some(t => t.value === formData.event_type)) {
+      setFormData(prev => ({ ...prev, event_type: availableEventTypes[0].value }));
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [availableEventTypes, formData.event_type]);
+
   // Fetch default settings
   const { data: settings } = useQuery({
     queryKey: ['admin-settings'],