feat(pricing): add competitor price comparison calculator
- Interactive slider for 50–10,000 members
- Real prices from SEWOBE, easyVerein, ClubDesk, WISO MeinVerein
- Bar chart comparing monthly/yearly costs
- Savings callout showing annual savings vs most expensive competitor
- Feature comparison table (Verband, Website, Kurse, SEPA, Support, etc.)
- SEWOBE Verband warning for 1000+ members
- Uses shadcn/ui components (Card, Badge, Button, Table)
- CTA linking to sign-up
- 4 tiers: Starter (29€), Pro (59€), Verband (199€), Enterprise (349€)
da862f2194