fix(images): drop forced upscaling, match live image sizes

The image macro was resizing every call to its width arg, including
upscaling 270x180 service thumbnails to 600x400 and rendering 400x400
doctor portraits at full size. Live serves service thumbs at native
270x180 (CSS-floated) and doctor portraits at 200x200.

- image macro: width=0 (default) skips resize, emits raw <img> with no
  width/height — lets theme CSS do the sizing, matching live pattern
- img shortcode: defaults width to 0 so callers can omit it
- service grid (home + 7 service pages): drop width=600
- doctor portraits on /team: width=200 (matches live render)

content/services/corona.md

@@ -6,7 +6,7 @@ weight = 20
 anchor = "Corona"
 +++
 
-{{ img(src="services/Corona.jpg", width=600, alt="Corona", class="float-right") }}
+{{ img(src="services/Corona.jpg", alt="Corona", class="float-right") }}
 
 Seit Beginn der Coronapandemie führen wir in unserer Praxis Tests auf das Corona-Virus (SARS-CoV-2) durch. 
 Zum Schutz aller Anwesenden werden Tests bei Patientinnen und Patienten **mit Symptomen**, sowie deren **Kontaktpersonen**, ausschließlich während