Starting gold input in millions with decimal support ✨ (#3349)

## Description:

**Starting gold input: use millions**

Changes the starting gold input in singleplayer and host lobby modals to
accept values in millions (e.g. enter `5` for 5M gold). Supports
decimals like `6.6` for 6.6M. The value is multiplied by 1,000,000
before being sent to the game config.

- Label updated to "Starting Gold (Millions)"
- Input uses float parsing with min 0.1, matching gold multiplier
behavior
- JoinLobbyModal shows clean values without unnecessary decimals (e.g.
"5M" not "5.00M")

Previous

<img width="215" height="139" alt="image"
src="https://github.com/user-attachments/assets/00ce5b6d-f74d-4aee-92f5-c9be1a0a6d3d"
/>
<img width="292" height="74" alt="image"
src="https://github.com/user-attachments/assets/4de936a3-22bd-4ffc-8dbe-0d5066f28186"
/>

Now

<img width="216" height="151" alt="image"
src="https://github.com/user-attachments/assets/489de13e-65b5-4b02-a654-5f6f74b165d1"
/>
<img width="292" height="72" alt="image"
src="https://github.com/user-attachments/assets/51723d5a-55ab-4b7b-bbce-011a586eeb44"
/>

## 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:

FloPinguin

src/client/Utils.ts

@@ -115,6 +115,8 @@ export interface ModifierInfo {
   badgeParams?: Record<string, string | number>;
   /** The raw value if applicable (e.g. startingGold amount) */
   value?: number;
+  /** Pre-formatted display string (used instead of renderNumber when provided) */
+  formattedValue?: string;
 }
 
 /**
@@ -150,13 +152,17 @@ export function getActiveModifiers(
     });
   }
   if (modifiers.startingGold) {
+    const millions = parseFloat(
+      (modifiers.startingGold / 1_000_000).toPrecision(12),
+    );
     result.push({
       labelKey: "host_modal.starting_gold",
       badgeKey: "public_game_modifier.starting_gold",
       badgeParams: {
-        amount: Math.round(modifiers.startingGold / 1_000_000),
+        amount: millions,
       },
       value: modifiers.startingGold,
+      formattedValue: `${millions}M`,
     });
   }
   return result;