Rework trains to encourage alliances (#1697)

## Description:

This update encourages alliances by modifying how train-based trading
works. Trading is now restricted to allied networks, and allied trades
offer better rewards than self-trades, incentivizing cooperation.

Changes:
- Train destinations are now limited to stations owned by the player or
their allies.
    - Delivering a train to one’s own station grants 4,000 gold.
- Delivering a train to an ally’s station grants 5,000 gold to both the
sender and the receiver.

This system encourages players to form alliances, especially with
factory-focused players.


## 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 have read and accepted the CLA agreement (only required once).

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

IngloriousTom

src/client/Utils.ts

@@ -5,24 +5,27 @@ export function renderTroops(troops: number): string {
   return renderNumber(troops / 10);
 }
 
-export function renderNumber(num: number | bigint): string {
+export function renderNumber(
+  num: number | bigint,
+  fixedPoints?: number,
+): string {
   num = Number(num);
   num = Math.max(num, 0);
 
   if (num >= 10_000_000) {
     const value = Math.floor(num / 100000) / 10;
-    return value.toFixed(1) + "M";
+    return value.toFixed(fixedPoints ?? 1) + "M";
   } else if (num >= 1_000_000) {
     const value = Math.floor(num / 10000) / 100;
-    return value.toFixed(2) + "M";
+    return value.toFixed(fixedPoints ?? 2) + "M";
   } else if (num >= 100000) {
     return Math.floor(num / 1000) + "K";
   } else if (num >= 10000) {
     const value = Math.floor(num / 100) / 10;
-    return value.toFixed(1) + "K";
+    return value.toFixed(fixedPoints ?? 1) + "K";
   } else if (num >= 1000) {
     const value = Math.floor(num / 10) / 100;
-    return value.toFixed(2) + "K";
+    return value.toFixed(fixedPoints ?? 2) + "K";
   } else {
     return Math.floor(num).toString();
   }

src/client/graphics/layers/FxLayer.ts

@@ -66,33 +66,27 @@ export class FxLayer implements Layer {
   }
 
   onBonusEvent(bonus: BonusEventUpdate) {
-    const tile = bonus.tile;
-    if (this.game.owner(tile) !== this.game.myPlayer()) {
+    if (this.game.player(bonus.player) !== this.game.myPlayer()) {
       // Only display text fx for the current player
       return;
     }
+    const tile = bonus.tile;
     const x = this.game.x(tile);
     let y = this.game.y(tile);
     const gold = bonus.gold;
     const troops = bonus.troops;
-    const workers = bonus.workers;
 
     if (gold > 0) {
-      const shortened = renderNumber(gold);
+      const shortened = renderNumber(gold, 0);
       this.addTextFx(`+ ${shortened}`, x, y);
       y += 10; // increase y so the next popup starts bellow
     }
 
     if (troops > 0) {
-      const shortened = renderNumber(troops);
+      const shortened = renderNumber(troops, 0);
       this.addTextFx(`+ ${shortened} troops`, x, y);
       y += 10;
     }
-
-    if (workers > 0) {
-      const shortened = renderNumber(workers);
-      this.addTextFx(`+ ${shortened} workers`, x, y);
-    }
   }
 
   addTextFx(text: string, x: number, y: number) {