KABUL, March 6 — Pakistani and Afghan troops exchanged fire at dozens of points along their border on Friday as the ​UN said their week-old conflict has forced the displacement of more than 100,000 people. The South Asian nations show no signs of rapprochement ‌in their worst fighting in years, adding to the volatility in a region also contending with US and Israeli strikes on Iran  — a nation that borders both Afghanistan and Pakistan. Combat has included Pakistani air strikes on Taliban