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.

ROADMAP.md

@@ -5,6 +5,7 @@ Open ideas for the playground frontend. Tick a box when done.
 ## Quick wins
 
 - [ ] **Labyrinth grid size crash**: `labyrinth.component.html` still binds `[gridRows]`; typed sizes above the max crash the page. Same fix as pathfinding (clamp in code, drop the binding).
+- [ ] **Fourier circles slider thumb**: at "Circles: 256" the thumb sits near the left end, like at 30. Check `max`/value binding of the circles `mat-slider` (seen 2026-10-14, not verified).
 - [ ] **Lighthouse gate**: add an `assert` block to `lighthouserc.json` (e.g. performance, accessibility, SEO >= 0.9). Today CI runs the audit but never fails.
   Note: the `@lhci/cli` → lighthouse 13 override in `package.json` is only safe without `assert`. Check it again before you add one.
 - [ ] **robots.txt + sitemap.xml**: static files in `public/`, listing all routes from `app.routes.ts`.