feat(fourier): add dog head preset

Build the dog outline from one mirrored right half.
Smooth it with Chaikin corner cutting (3 passes).
Also add a ROADMAP note for the circles slider thumb.

src/assets/i18n/de.json

@@ -679,6 +679,7 @@
     "PRESET_HEART": "Herz",
     "PRESET_STAR": "Stern",
     "PRESET_SQUARE": "Quadrat",
+    "PRESET_DOG": "Hund",
     "CIRCLES": "Kreise",
     "SPEED": "Geschwindigkeit",
     "SHOW_CIRCLES": "Kreise anzeigen",