Improve admin candidate modal UX and add clip menu visibility toggle

- Widen AdminCandidateEditorModal to size lg for better readability
- Rename "Clip-Compilation" section to "Clip / Compilation", update copy to reflect single clips too, drop upload hint and Clip-Plattform field, rename label to "Link"
- Fix NativeSelect dropdown clipping inside overflow-y-auto modals by teleporting the menu to body with fixed positioning, flip-up logic, and dynamic maxHeight capped to viewport
- Add ClipAdminMenuVisible setting (backend domain, contracts, endpoint, migration) with matching frontend types, defaults, form wiring, and toggle in the Clip-Workflow modal — hides the Clips nav item from the admin sidebar when disabled

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

Backend/Data/SeedSiteSettingsBootstrapper.cs

@@ -41,6 +41,26 @@ public static partial class SeedDataBootstrapper
             settings.RiskRulesJson = RiskRuleSettings.Serialize(RiskRuleSettings.Defaults);
         }
 
+        if (!HasValidWorkflowRules(settings.WorkflowRulesJson))
+        {
+            settings.WorkflowRulesJson = WorkflowRuleSettings.Serialize(WorkflowRuleSettings.Defaults);
+        }
+
+        if (!HasValidNominationLinkBlacklist(settings.NominationLinkBlacklistJson))
+        {
+            settings.NominationLinkBlacklistJson = NominationLinkBlacklistSettings.Serialize(NominationLinkBlacklistSettings.Defaults);
+        }
+
+        if (string.IsNullOrWhiteSpace(settings.ClipSubmissionDisabledMessage))
+        {
+            settings.ClipSubmissionDisabledMessage = "Clip-Einreichungen sind aktuell geschlossen.";
+        }
+
+        if (string.IsNullOrWhiteSpace(settings.ShowactApplicationDisabledMessage))
+        {
+            settings.ShowactApplicationDisabledMessage = "Showact-Bewerbungen sind aktuell geschlossen.";
+        }
+
         if (string.IsNullOrWhiteSpace(settings.ImprintContent))
         {
             settings.ImprintContent = SeedCatalog.DefaultImprintContent;
@@ -55,6 +75,16 @@ public static partial class SeedDataBootstrapper
         {
             settings.SponsorsContent = SeedCatalog.DefaultSponsorsContent;
         }
+
+        if (string.IsNullOrWhiteSpace(settings.ShowactsUrl))
+        {
+            settings.ShowactsUrl = "https://vtuber-star-awards.de/showacts";
+        }
+
+        if (string.IsNullOrWhiteSpace(settings.ShowactsContent))
+        {
+            settings.ShowactsContent = "Informationen zu Showact-Bewerbungen, Ablauf und Kontakt fuer die Award-Show.";
+        }
     }
 
     private static bool HasValidSiteArray(string? json, params string[] requiredKeys)
@@ -87,4 +117,30 @@ public static partial class SeedDataBootstrapper
 
     private static bool HasValidRiskRules(string? json) =>
         RiskRuleSettings.Read(new Backend.Domain.SiteSettings { RiskRulesJson = json ?? string.Empty }).Length == RiskRuleSettings.Defaults.Length;
+
+    private static bool HasValidWorkflowRules(string? json) =>
+        WorkflowRuleSettings.Read(new Backend.Domain.SiteSettings { WorkflowRulesJson = json ?? string.Empty }).Length == WorkflowRuleSettings.Defaults.Length;
+
+    private static bool HasValidNominationLinkBlacklist(string? json)
+    {
+        if (string.IsNullOrWhiteSpace(json))
+        {
+            return false;
+        }
+
+        try
+        {
+            using var document = JsonDocument.Parse(json);
+            return document.RootElement.ValueKind == JsonValueKind.Array
+                && document.RootElement.EnumerateArray().Any(item =>
+                    item.ValueKind == JsonValueKind.Object
+                    && item.TryGetProperty("Url", out var url)
+                    && url.ValueKind == JsonValueKind.String
+                    && !string.IsNullOrWhiteSpace(url.GetString()));
+        }
+        catch (JsonException)
+        {
+            return false;
+        }
+    }
 }