Feat: Display ghost railways when building cities and ports (#3202)

## Description:

Based on [this suggestion on
Discord](https://discord.com/channels/1284581928254701718/1447110257196138577)
and feedback gathered in [this
thread](https://discord.com/channels/1359946986937258015/1469598906173227184).

Supersedes #3143 

This PR introduces "ghost railways": when you are going to place a city
or port, previews railway connections that will be made when actually
building the structure.

Ghost railways are skipped if the structure is going to be snapped to
existing railways (as in railway snapping functionality introduced in
#3156 ).

### Video


https://github.com/user-attachments/assets/ff8cf325-6501-4df8-801d-c8ae3ced3d0e


### Ghost rails color revisited

black with 40% opacity

<img width="695" height="430" alt="image"
src="https://github.com/user-attachments/assets/272efbcc-4185-426a-921c-7fae61f6c462"
/>


## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

deshack_82603

tests/InputHandler.test.ts

@@ -39,6 +39,7 @@ describe("InputHandler AutoUpgrade", () => {
         ghostStructure: null,
         rocketDirectionUp: true,
         overlappingRailroads: [],
+        ghostRailPaths: [],
       },
       mockCanvas,
       eventBus,