Add pendulum demo and WGSL support

Introduce a new Pendulum demo (component, template, stylesheet) and wire it into routing and the algorithms list. Extend Babylon canvas API to emit a SceneReadyEvent (scene + engine) and accept a shaderLanguage option in RenderConfig so materials/shaders can target WGSL; update Fractal to consume the new SceneReadyEvent signature. Also add i18n entries for the pendulum demo.

src/assets/i18n/en.json

@@ -440,6 +440,10 @@
       "TITLE": "Fractals 3D",
       "DESCRIPTION": "3D Visualisation of complex geometric patterns that resemble each other on increasingly smaller scales (self-similarity)."
     },
+    "PENDULUM": {
+      "TITLE": "Pendulum",
+      "DESCRIPTION": "Just a test atm."
+    },
     "NOTE": "Note",
     "GRID_HEIGHT": "Height",
     "GRID_WIDTH": "Width"