Migrated all six service pages from Grav to Zola format:
- YAML frontmatter → TOML with weight and extra.anchor
- Grav image refs → {{ img() }} shortcode calls
- [fa=external-link /] → <i class="fa fa-external-link"></i>
- Linked image in HV page wrapped with <a href> HTML tag
Anchors HV, Corona, Vorsorge, Diagnostik, Kardio, Diabetologie match
the home page service grid links established in commit 9cf54f9.
Brummel