chore(assets): trocar PNGs do logo por SVGs vetorizados

- adiciona public/images/logo_small.svg e logo_text.svg com width/height
  explícitos (necessário para naturalWidth/Height funcionar via <img>)
- remove os PNGs antigos (logo_small.png e logo_text.png)
- atualiza referência no README.md (header) para logo_small.svg

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

public/images/logo_small.svg

@@ -0,0 +1,3 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200" viewBox="0 0 200 200" role="img" aria-label="OpenMonetis">
+  <path fill="#ff7733" d="M 77.66,165.64 L 37.77,141.54 L 63.30,108.72 L 27.13,97.44 L 46.81,50.77 L 77.66,63.08 L 81.91,30.26 L 126.40,29.23 L 126.06,33.85 L 122.87,67.69 L 158.51,50.77 L 178.19,90.26 L 140.96,104.62 L 162.23,127.18 L 132.98,162.56 L 103.19,131.79 Z"/>
+</svg>