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/Endpoints/AdminSeasonResultsEndpoints.cs

@@ -36,6 +36,40 @@ public static partial class AdminSeasonManagementEndpoints
             return Results.BadRequest(new { message = "The selected candidate does not belong to the selected category." });
         }
 
+        var workflowRules = await LoadWorkflowRulesAsync(db, context.RequestAborted);
+        var winnerRequiresClipRule = WorkflowRuleSettings.Find(workflowRules, WorkflowRuleSettings.WinnerRequiresClip);
+        if (WorkflowRuleSettings.ShouldBlock(winnerRequiresClipRule)
+            && string.IsNullOrWhiteSpace(candidate.ClipCompilationUrl))
+        {
+            return CreateWorkflowRuleError(
+                "Dieser Kandidat hat noch keinen gepflegten Clip-Link. Bitte zuerst die Clip-Compilation am Kandidaten hinterlegen oder die Workflow-Regel umstellen.");
+        }
+
+        var winnerPlacementsRule = WorkflowRuleSettings.Find(workflowRules, WorkflowRuleSettings.MaxWinnerPlacements);
+        if (WorkflowRuleSettings.ShouldBlock(winnerPlacementsRule))
+        {
+            var candidateIdentityKey = WorkflowRuleSettings.CandidateIdentityKey(candidate);
+            var existingWinnerIdentities = await db.Results
+                .AsNoTracking()
+                .Include(item => item.Candidate)
+                .Where(item => item.SeasonId == seasonId && item.CategoryId != request.CategoryId)
+                .Select(item => new
+                {
+                    item.CategoryId,
+                    item.Candidate.DisplayName,
+                    item.Candidate.ChannelSlug,
+                })
+                .ToArrayAsync(context.RequestAborted);
+            var existingWinnerCount = existingWinnerIdentities.Count(item =>
+                string.Equals(WorkflowRuleSettings.CandidateIdentityKey(item.DisplayName, item.ChannelSlug), candidateIdentityKey, StringComparison.Ordinal));
+
+            if (existingWinnerCount >= winnerPlacementsRule.Limit)
+            {
+                return CreateWorkflowRuleError(
+                    $"Diese Person hat bereits {existingWinnerCount} Gewinnerplatz(e). Limit: {winnerPlacementsRule.Limit}.");
+            }
+        }
+
         var existingResult = await db.Results.FirstOrDefaultAsync(item =>
             item.SeasonId == seasonId
             && item.CategoryId == request.CategoryId);