fix(payout): hold ambiguous transfers, close announce/cancel races, review follow-ups

[CodeWithEugene]

Follow-ups from the review of #52, plus two auth UI tweaks.

Money path

• executePayout stores the attempt reference when it claims the payout. If the transfer call throws (timeout, dropped connection), it asks Paystack about that attempt before deciding: success confirms, failed/reversed/not_found retries, pending/unknown holds PROCESSING for the sweep. This removes a double-pay window. The Paystack port gains a not_found status.
• announceWinners and both cancel paths use conditional status updates, so a cancel racing an announce can't both succeed.

Security and ops

• Per-action rate-limit keys (register, event-cancel, judge-invite) instead of one shared mutate: counter.
• Hourly purge of expired RateLimitBucket rows.
• /api/health returns 503 when the payment or chain port can't resolve.
• CSP connect-src allows the Sentry ingest origin from the public DSN.
• Removed the unused direct pg dependency.

SEO and copy

• robots.txt blocks /organizer and /organizer/ without hiding the public /organizers/<slug> pages.
• Removed em/en dashes from user-facing strings; Title Case fixes.

Auth UI

• Auth form cards are square and span the ruled column, so their top and bottom rules meet the vertical hairlines. Sign-in and sign-up headings are centered.
• Every password field (sign in, sign up, reset, account settings) gets a show/hide toggle.

Test plan

• tsc --noEmit, lint, build
• pnpm test: 471 tests, including new ones for the ambiguous-transfer matrix, not_found/unknown/success after a thrown transfer, both race guards (verified failing without the guards), and the rate-limit purge
• Auth pages checked in the browser at 1440px and 375px, light and dark