fika-leaderboard capture sink

Operator routes (not recorded):
  GET /healthz         liveness + capture dir
  GET /captures[?n=N]  total count + the N most recent captures (newest first)

Everything else is recorded verbatim and answered so the SPT-Leaderboard mod stays quiet.
Point the mod here:  SPTLB Server Endpoint = <this origin>   Server Path = /api/main/
Runbook: docs/playbooks/capture-raid-payloads.md