termin 2: fix course number 223015c → 223015b, add frontpage footer,
fix email, convert aufgaben to fleißaufgaben (no forum)
termin 4: add frontpage footer, fix email, convert aufgaben to
fleißaufgaben (no forum), update 9 wochen → 5 termine structure
termin 5: rebuild frontpage with course info and git link, fix email
- extract _frontmatter.md, _intro.md, _outro.md as shared components
- create separate files per termin with date-topic naming convention:
2025-12-19-termin-1-grundlagen-text-audio.md
2026-01-09-termin-2-bild-audio-video.md
2026-01-23-termin-3-speichermedien-schnittstellen.md
2026-01-30-termin-4-distribution-apis-zukunft.md
2026-xx-xx-termin-5-vertiefung-offene-fragen.md
- keep index.md.bak as backup (gitignored)