=== ghost-0001: getReferrersHistory O(P*A) -> O(P+A) ===

                 scale    defective      fixed    speedup
------------------------------------------------------------
  A=  1500 P= 100       4.75ms     0.31ms     15.4x
  A=  6000 P= 200      42.47ms     1.30ms     32.7x
  A= 18000 P= 300     193.68ms     3.65ms     53.0x
  A= 36000 P= 500     693.20ms     7.30ms     95.0x
  A=109500 P=1000    4202.31ms    22.88ms    183.7x

Conclusion: O(P*A) -> O(P+A) — Map<source|date, entry> hoist.
Long-running Ghost sites (200+ sources, year of dates) hit 100k+ entries.
