Trim hero section and homepage copy

[PianoNic]

Simplify the homepage hero and tidy up copy:

• Shorten the hero subtitle in all five languages (de, en, fr, it, rm)
• Remove the "Offen / Schulnetz, OdaOrg ..." pill bar
• Remove the GitHub-stars / downloads / platforms stats bar
• Remove the hero startup entrance animation
• Rename German CTA "Schuly holen" -> "Schuly herunterladen"
• Add the Docs link to the footer (not only the top nav)
• Fix the FAQ closed-state bottom gap (collapsed item kept ~20px padding height)