Add unlink flow for linked games

Endpoints/AdminEndpoints.cs

@@ -124,6 +124,61 @@ public static class AdminEndpoints
             });
         });
 
+        admin.MapPost("/unlink-suggestions", async ([FromBody] UnlinkSuggestionsRequest request, HttpContext ctx, AppDbContext db, IConfiguration config) =>
+        {
+            var player = await EndpointHelpers.GetAuthenticatedPlayer(ctx, db);
+            if (player is null || !await EndpointHelpers.IsAdmin(ctx, db, config)) return Results.Unauthorized();
+
+            var phase = await EndpointHelpers.GetPhase(db, player.Id);
+            if (phase != Phase.Vote)
+                return EndpointHelpers.PhaseMismatch(Phase.Vote, phase);
+
+            var suggestions = await db.Suggestions.ToListAsync();
+            var target = suggestions.FirstOrDefault(s => s.Id == request.SuggestionId);
+            if (target is null)
+                return Results.NotFound(new { error = "Suggestion not found." });
+
+            var rootIndex = EndpointHelpers.BuildLinkRoots(suggestions.Select(s => (s.Id, s.ParentSuggestionId)));
+            if (!rootIndex.TryGetValue(target.Id, out var rootId))
+                return Results.Ok(new { UnlinkedSuggestionIds = Array.Empty<int>(), UnfinalizedPlayers = 0 });
+
+            var groupIds = rootIndex
+                .Where(kv => kv.Value == rootId)
+                .Select(kv => kv.Key)
+                .ToList();
+
+            await using var tx = await db.Database.BeginTransactionAsync();
+
+            foreach (var suggestion in suggestions.Where(s => groupIds.Contains(s.Id)))
+            {
+                suggestion.ParentSuggestionId = null;
+            }
+
+            await db.SaveChangesAsync();
+
+            var affectedPlayerIds = await db.Votes
+                .Where(v => groupIds.Contains(v.SuggestionId))
+                .Select(v => v.PlayerId)
+                .Distinct()
+                .ToListAsync();
+
+            await db.Votes.Where(v => groupIds.Contains(v.SuggestionId)).ExecuteDeleteAsync();
+
+            if (affectedPlayerIds.Count > 0)
+            {
+                await db.Players.Where(p => affectedPlayerIds.Contains(p.Id))
+                    .ExecuteUpdateAsync(p => p.SetProperty(x => x.VotesFinal, false));
+            }
+
+            await tx.CommitAsync();
+
+            return Results.Ok(new
+            {
+                UnlinkedSuggestionIds = groupIds,
+                UnfinalizedPlayers = affectedPlayerIds.Count
+            });
+        });
+
         admin.MapPost("/reset", async (HttpContext ctx, AppDbContext db, IConfiguration config) =>
         {
             if (!await EndpointHelpers.IsAdmin(ctx, db, config)) return Results.Unauthorized();