bug fix?: Hide UnitDisplay frame when all unit types are disabled (#1392)

## Description:

This PR updates the UnitDisplay component so that when all unit types
(City, Factory, Port, Defense Post, Missile Silo, SAM Launcher) are
disabled in the game config, the UI frame itself will also be hidden.

This is a box that shows how many and what types of units the player
currently owns.
There’s a feature where, if unit types are disabled in the settings, the
corresponding parts of the UI will disappear.

However, if all unit types are disabled, for some reason the outer
container still remains visible.
While this might not be a critical issue, I feel it’s unnecessary and
redundant, so I’d like to remove it.

Alternatively, we could consider keeping the box as a kind of
placeholder to indicate that some kind of menu might appear there.
But since it serves no purpose during gameplay in that state, I think it
would just be meaningless UI.

before
<img width="1049" alt="スクリーンショット 2025-07-10 12 49 37"
src="https://github.com/user-attachments/assets/b0cf12ba-0c20-4b21-bf9f-cb17fec6817b"
/>
<img width="44" alt="スクリーンショット 2025-07-10 12 49 47"
src="https://github.com/user-attachments/assets/61e1960b-56d4-4dc8-80e7-27e49cb2d0e3"
/>

after
<img width="967" alt="スクリーンショット 2025-07-10 12 48 08"
src="https://github.com/user-attachments/assets/dfc90243-e4d6-4663-bff5-5be34453e80b"
/>

## 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
- [x] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

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

aotumuri

src/client/graphics/layers/UnitDisplay.ts

@@ -24,12 +24,21 @@ export class UnitDisplay extends LitElement implements Layer {
   private _port = 0;
   private _defensePost = 0;
   private _samLauncher = 0;
+  private allDisabled = false;
 
   createRenderRoot() {
     return this;
   }
 
   init() {
+    const config = this.game.config();
+    this.allDisabled =
+      config.isUnitDisabled(UnitType.City) &&
+      config.isUnitDisabled(UnitType.Factory) &&
+      config.isUnitDisabled(UnitType.Port) &&
+      config.isUnitDisabled(UnitType.DefensePost) &&
+      config.isUnitDisabled(UnitType.MissileSilo) &&
+      config.isUnitDisabled(UnitType.SAMLauncher);
     this.requestUpdate();
   }
 
@@ -89,6 +98,10 @@ export class UnitDisplay extends LitElement implements Layer {
       return null;
     }
 
+    if (this.allDisabled) {
+      return null;
+    }
+
     return html`
       <div
         class="fixed bottom-4 left-1/2 transform -translate-x-1/2 z-[1100] bg-gray-800/70 backdrop-blur-sm border border-slate-400 rounded-lg p-2 hidden lg:block"