Add cloth simulation page with WGSL shaders

Introduce a new cloth simulation feature: adds ClothComponent (TS/HTML/SCSS) and WGSL compute/vertex/fragment shaders implementing an XPBD-based cloth sim. Wire up routing and RouterConstants, add the cloth entry to the algorithms list, and add English/German i18n strings. Also include small refactors/renames for algorithm-category and algorithms.service imports and update BabylonCanvas to tolerate optional shader configuration and avoid null access during setup.

src/assets/i18n/de.json

@@ -471,6 +471,9 @@
       "DISCLAIMER_BOTTOM": "HINWEIS: Wenn zuviele Impulse in das System gegeben werden, wird die Simulation instabil. Dann hängt das Pendel nur noch runter und es muss neu gestartet werden."
     }
   },
+  "CLOTH": {
+    "TITLE": "Stoff-Simulation"
+  },
   "ALGORITHM": {
     "TITLE": "Algorithmen",
     "PATHFINDING": {
@@ -501,6 +504,10 @@
       "TITLE": "Doppel-Pendel",
       "DESCRIPTION": "Visualisierung einer chaotischen Doppel-Pendel-Simulation mit WebGPU."
     },
+    "CLOTH": {
+      "TITLE": "Stoff-Simulation",
+      "DESCRIPTION": "Simulation on Stoff mit WebGPU."
+    }
     "NOTE": "HINWEIS",
     "GRID_HEIGHT": "Höhe",
     "GRID_WIDTH": "Beite"