Single bounty page UI

[spherical-spinach]

Summary

This PR adds single bounty page UI with Bounty information panel and Discussion section. It also adds routing from front page bounty cards, redirecting clicks to the corresponding single bounty page.

Related issue

Closes #30

Changes made

• Added link from landing page BountyCard to single bounty page
• Moved mock data from src/routes/+page.svelte to src/lib/mock/bounties.ts
• Added new mock data to demonstrate the new single bounty page UI properly.
• Updated bounty types for new mock data
• Added src/routes/bounties/[id]/+page.svelte to render single bounty page UI

Author checklist

bun run pr runs all the commands below in one go.

• Matches the spec
• bun run format - code has been formatted
• bun run lint - no prettier/eslint errors
• bun run check - no svelte-check/TypeScript errors
• bun run test - all tests pass
• bun run build - build succeeds
• I tested the relevant changes manually

Reviewer manual testing checklist

• Clicking landing page Bounty cards redirects to single bounty page
• Nostr login links are disabled
• Clicking "All bounties" link redirects back to landing page
• Clicking a landing page Bounty card renders the right bounty as a single bounty page
• bun pr passes

[lambdakilo]

LGTM!