feat(algorithms): add how-it-works and source links

Add idea, complexity, data structures, GPU use to 10 algorithm pages.
Link logic files on Gitea; a spec fails on a missing path.
Fix wrong texts: cloth phases, pendulum dt, fractal lighting, typos.

src/app/constants/UrlConstants.ts

@@ -26,5 +26,6 @@
   static readonly FOUR_COLOR_THEOREM = 'https://de.wikipedia.org/wiki/Vier-Farben-Satz'
   static readonly FOURIER_SERIES_WIKI = 'https://de.wikipedia.org/wiki/Fourierreihe'
   static readonly GITEA = 'https://git.andreas-dahm.eu'
+  static readonly PLAYGROUND_SOURCE_BASE = `${UrlConstants.GITEA}/Lobo_Corp/playground-frontend/src/branch/main/`
 
 }