fix #3057: route AlreadyExists uploads to /content/maps/ not /content/games/

Re-uploading an existing map dropped the file into /content/games/, so
BuildLinks (which probes /content/maps/) never saw it and LinkCount stayed
0 — the "WILL NOT BE DOWNLOADABLE" the ticket describes.

Root cause: `res.ResourceInfo is Map` was the subfolder discriminator.
On the AlreadyExists path UnitSyncer skips GetResourceFromFileName and
returns the plain ResourceInfo from ArchiveCache (ArchiveCache.cs:36
constructs them as `new ResourceInfo() { ... }`, not Map), so the check
is silently false. Only the brand-new-registration path produced a Map
instance, so only new-map uploads ever worked.

Verified empirically against live zero-k.info — all 5 maps from the
ticket are sitting at /content/games/{name}.sd7 (200 OK) instead of
/content/maps/. Other casualties found via the same scan:
Hide_and_Seek_2.2.3, Coastlines_Dry_V2.2, Supreme_Crossing_V1.

Fix: derive `isMap` from `resource.TypeID == ResourceType.Map` (DB is
the source of truth; we're already loading `resource` in this scope).
Keep `is Map` as the fallback for the very first registration of a new
map where the DB row doesn't exist yet at the point of subfolder choice.

Stranded files at /content/games/ are left in place — a re-upload after
deploy puts them at the correct path. Cleanup of orphans deferred.

Author: Licho1

Zero-K.info/Controllers/MapsController.cs

@@ -452,14 +452,21 @@ public ActionResult UploadResource(HttpPostedFileBase file, bool specialMap)
                 {
                     if (res.Status != UnitSyncer.ResourceFileStatus.RegistrationError)
                     {
-                        var subfolder = (res.ResourceInfo is Map) ? "maps" : "games";
-                        var contentFolder = Path.Combine(Server.MapPath("~/content"), subfolder);
-                        if (!Directory.Exists(contentFolder)) Directory.CreateDirectory(contentFolder);
-
                         // refresh mirrors (local + springfiles)
                         using (var db = new ZkDataContext())
                         {
                             var resource = db.Resources.FirstOrDefault(x => x.InternalName == res.ResourceInfo.Name);
+
+                            // Subfolder from DB type. Don't use `res.ResourceInfo is Map`: on the
+                            // AlreadyExists path the archive cache hands us a plain ResourceInfo (not
+                            // the Map subclass), so that check is silently false and files land in
+                            // /content/games/ instead of /content/maps/ — see issue #3057.
+                            var isMap = resource?.TypeID == ResourceType.Map
+                                        || (resource == null && res.ResourceInfo is Map);
+                            var subfolder = isMap ? "maps" : "games";
+                            var contentFolder = Path.Combine(Server.MapPath("~/content"), subfolder);
+                            if (!Directory.Exists(contentFolder)) Directory.CreateDirectory(contentFolder);
+
                             // case-insensitive FileName match: DB row may have different casing than the
                             // freshly-uploaded file (springfiles vs original-upload casing) — see issue #3052
                             var contentFile = resource?.ResourceContentFiles.FirstOrDefault(