feat: complete route tier hierarchy with type tags and new generators

Add type annotations to all route generators and introduce intermediate
tiers: town roads (regional centers, 40km), footpaths (hamlets, 15km),
and major sea routes (capital/large ports, MST). Reorder generation to
royal→main→market→town→trails→footpaths→majorSea→sea→air. Add main road
tier modifier (0.6) and border penalty exemption.

Author: barrulus