Fix PTB ZoneSystem APIs

[jneb802]

Summary

• Let the AIO port manager use the PTB GetLocationList return type without hard-coding the old Vector2i dictionary key.
• Update Forbidden_Catacombs and Underground_Ruins sector lookup code from Vector2i/ZDOMan.SectorToIndex to the PTB Vector2s/ZoneSystem.SectorToIndex API.

Validation

• Built the main AIO project against the PTB server assembly mirror:
  dotnet build MoreWorldLocations_All.sln /p:VALHEIM_INSTALL=/Users/benjmarston/Develop/valheim-ptb-server /p:BepInExPath="/Users/benjmarston/Library/Application Support/Steam/steamapps/common/Valheim/BepInEx" /p:BEPINEX_PATH="/Users/benjmarston/Library/Application Support/Steam/steamapps/common/Valheim/BepInEx"
• Deployed More_World_Locations_AIO.dll to Hetzner praetoris PTB test server.
• Confirmed deployed DLL SHA256: a270695ed353a1dbc55bfc09292da92540347745711f503897d5aa6034764f38.
• Restarted test server through mmcli-agent with 0 players online.

Notes

• The two dungeon source fixes are included, but their legacy non-SDK project files do not currently build on this Mac: dotnet can be pointed at the .NET Framework reference assemblies, but Jotunn/YamlDotNet/package references do not resolve cleanly under those projects. They should still be built in the normal Windows/release environment before publishing dungeon DLLs.
• Dedicated-server validation covers the active AIO DLL; client-side PTB testing is still needed for location and port behavior.

[jneb802]

Final Hetzner PTB validation after the last restart: BepInEx loads More_World_Locations_AIO 4.7.3, Forbidden_Catacombs 1.0.2, and Underground_Ruins 1.0.7. No MoreWorldLocations-targeted errors found in the targeted log scan. The remaining GetRandomPointInZone(Vector2i, float) warning is emitted immediately after Expand World Data 1.63 loads, so it is not from this plugin.