Also drops confirmed-dead code found during extraction: unused TIER1_ASNS
require (its only consumer, computeRouteLeakDetection, already moved to
server/route-leak.js with its own require) and bgproutesVpCache/
bgproutesVpCacheTs/BGPROUTES_VP_TTL (declared, never read anywhere).
Verified via smoke-test harness (28/28 match). server.js: 6302 -> 5907 lines.
