Combines the local SQLite bridge (getPdbLocal/queryPeeringDBLocal, was at
the very top of the file) with the live-API fetch helpers (fetchPeeringDB/
fetchPeeringDBWithRetry/pdbSemaphore, ~950 lines further down) into one
module -- they were always one logical unit (queryPeeringDBLocal is only
ever called from fetchPeeringDB).
Verified via smoke-test harness (28/28 match). server.js: 5018 -> 4827 lines.
