Coordinate grid (#4224)

**Add approved & assigned issue number here:**

Resolves #3839

## Description:
A bunch of small updates to make the coordinate grid a lot nicer.
 - Removes black backgrounds on text.
 - Allows user to modify the opacity of the coordinate grid
 - Persist the enable state of the coordinate grid

### Before
<img width="2344" height="1168" alt="image"
src="https://github.com/user-attachments/assets/22c2fb77-9db6-41bf-a50a-987f651cc19a"
/>

### After
<img width="2331" height="1174" alt="image"
src="https://github.com/user-attachments/assets/0e5a9575-8a79-407b-8d78-8564df02b259"
/>

<img width="407" height="947" alt="image"
src="https://github.com/user-attachments/assets/b9e5f9f1-3cc1-4832-b7d4-38e1f5e93d57"
/>

## 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

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

FrederikJA

resources/lang/en.json

@@ -972,6 +972,8 @@
     "territory_sat_desc": "How vivid the territory fill colors are (lower mutes them)",
     "territory_alpha_label": "Territory opacity",
     "territory_alpha_desc": "How opaque the territory fill is (lower lets terrain show through)",
+    "coordinate_grid_opacity_label": "Coordinate grid opacity",
+    "coordinate_grid_opacity_desc": "How opaque the coordinate grid is (lower lets more things show through)",
     "rail_distance_label": "Train track draw distance",
     "rail_distance_desc": "How far zoomed out train tracks remain visible",
     "rail_thickness_label": "Train track thickness",