coturn: allocate 256 ports instead of 16

hosts/by-name/servo/services/coturn.nix

@@ -31,9 +31,11 @@
 #   - this approach would fail the prosody conversations.im check, but i didn't notice *obvious* call routing errors.
 { lib, ... }:
 let
-  # TURN port range (inclusive)
-  turnPortLow = 49152;
-  turnPortHigh = 49167;
+  # TURN port range (inclusive).
+  # default coturn behavior is to use the upper quarter of all ports. i.e. 49152 - 65535.
+  # i believe TURN allocations expire after either 5 or 10 minutes of inactivity.
+  turnPortLow = 49152; # 49152 = 0xc000
+  turnPortHigh = turnPortLow + 256;
   turnPortRange = lib.range turnPortLow turnPortHigh;
 in
 {