Add events.gateway-gamers.net: upcoming events across BCP circuits

New 5th site in the monorepo, following the same shared header/footer/
images pattern as the others. Shows upcoming events for a configurable
list of BCP circuits (CONFIG.circuits in sites/events/src/main.js) —
adding a circuit is a one-line edit.

Data comes from the BCP API (`GET /v1/events?leagueId=<circuitId>`,
same auth-free headers the other sites already use) — "circuit" in
BCP's frontend URLs maps to `leagueId` in the API, confirmed via
/v1/leagues/<id> returning circuitLeague: true. Paginates newest-date-
first and stops once a full page has entirely concluded, so it doesn't
walk a circuit's whole history just to find the handful of upcoming
events. Verified against the live API for all 4 configured circuits
before writing this commit.

Nav cross-links with scouting only (per request), not the other 3
sites. nginx conf follows the same shared-asset-alias pattern as the
rest; TLS/DNS for the new subdomain still need to be provisioned
before it can go live (see follow-up).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SBzcNkW7JcYipnAX6HfgmK

sites/events/public/footer.html

@@ -0,0 +1 @@
+../../../shared/footer.html