chore(migrations): rename 013_bounties.sql to 014_bounties.sql

[biwasxyz]

Summary

Resolves a filename collision in migrations/:

• 013_identity_cache.sql (merged in feat(762b): migrate BNS + identity cache from KV to D1 + caches.default #852, landed first on main)
• 013_bounties.sql (merged in feat(bounty): native bounty system — replaces bounty.drx4.xyz proxy #843)

Both PRs picked 013_ as the next free slot while the other was in flight. Wrangler tracks applied migrations by full filename so both would have run, but the duplicate slot number is confusing for anyone reading the history.

Already applied

I applied this to remote D1 already as 014_bounties.sql (the bounty page was throwing "database is temporarily unavailable" on aibtc.com because the table didn't exist yet):

$ npx wrangler d1 migrations apply landing-page --remote
014_bounties.sql ✅

So the on-disk filename on main after this merge will match what's already recorded in the remote d1_migrations tracking table — wrangler won't try to re-apply.

Test plan

• CI green
• After merge: npx wrangler d1 migrations list landing-page --remote shows zero pending
• /bounty on aibtc.com loads (already confirmed via curl https://aibtc.com/api/bounties?limit=1 returning 200)