fix(fractal): keep non-escaping points black

Points that never escape kept the last loop index as iter, so they
never reached the black color. Start iter at maxIterations and set it
only when a point escapes. Update the ITEM_4 text (en, de) to match.

src/app/pages/algorithms/fractal/fractal.shader.ts

@@ -124,6 +124,7 @@ export const FRACTAL2D_FRAGMENT = `
             }
         }
         else { // Mandelbrot (0), Julia (1), Burning Ship (2)
+            iter = maxIterations; // stays at max for points that never escape (black interior)
             for(int i=0; i<2000; i++) {
                 if (i >= maxIterations) break;
 
@@ -134,7 +135,6 @@ export const FRACTAL2D_FRAGMENT = `
                     iter = i;
                     break;
                 }
-                iter = i;
 
                 if (algorithm == 2) { // Burning Ship
                     z.y = abs(z.y);