[FRONTEND] Swim logging page

[yrska]

🎯 Acceptance Criteria

• A new page with the route /swims
• Adds a new "Swims" entry to the hamburger/mobile nav menu only which links to this route
• Has a hero header section with the title "SWIMS". This should follow the existing hero/headers
• Form includes fields for member name, date, river/location, and optional notes
• Uses existing form input styling from the design system
• Client-side validation on required fields (name, date, location)
• No submission logic yet — this ticket is UI only

---

📊 Definition of Done (DoD)

• Acceptance criteria met
• Agreed tests written
• Agreed documentation in GitHub wiki
• PR reviewed

---

🔗 Dependencies

---

📚 Additional Context