Feat/stairs fence update (#226)

* feat: railing on the straight stairs and new fence

* feat: added spiral and curved stairs with bug fix for fence

* feat:fence are linked to each other ... so moving one move the other sharing the same coordinate

* fix: update stair railing logic to include front-side attachments for terminal landings

* Integrate fence rendering into the fence system

* fix: pass nodeId instead of undefined node to WallTreeNode and FenceTreeNode

TreeNode was passing `node` (undefined variable) instead of `nodeId` to
WallTreeNode and FenceTreeNode, causing a runtime ReferenceError.
Updated FenceTreeNode to accept nodeId and look up the node from the
scene store internally, consistent with all other tree node components.

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

* feat: update fence icon with new isometric design

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

---------

Co-authored-by: Aymeric Rabot <aymeric@pascal.app>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

bun.lock

@@ -48,7 +48,7 @@
     },
     "packages/core": {
       "name": "@pascal-app/core",
-      "version": "0.4.0",
+      "version": "0.5.0",
       "dependencies": {
         "dedent": "^1.7.1",
         "idb-keyval": "^6.2.2",
@@ -166,7 +166,7 @@
     },
     "packages/viewer": {
       "name": "@pascal-app/viewer",
-      "version": "0.4.0",
+      "version": "0.5.0",
       "dependencies": {
         "polygon-clipping": "^0.15.7",
         "zustand": "^5",