feat: roller coaster logo and working favicon

- public/logo.svg: amber coaster silhouette (lift hill + vertical loop +
  camelback) on transparent background; used in header and README
- app/icon.tsx: PNG favicon via Next.js ImageResponse (works in all
  browsers including Safari); renders simplified hill + loop on dark
  rounded-square background
- app/page.tsx: logo img added next to "Thoosie Calendar" title in header
- README.md: logo displayed at top of document
- Remove app/icon.svg (replaced by icon.tsx → PNG)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -1,5 +1,7 @@
 # Thoosie Calendar
 
+<img src="public/logo.svg" alt="Thoosie Calendar" width="320">
+
 A week-by-week calendar showing operating hours for all Six Flags Entertainment Group theme parks — including the former Cedar Fair parks. Data is scraped from the Six Flags internal API and stored locally in SQLite. Click any park to see its full month calendar and live ride status with current wait times.
 
 ## Parks