Refactor: Centralisation des constantes de configuration

**Motivations:**
- Éviter la duplication de code pour la lecture des configurations
- Centraliser les valeurs par défaut

**Root causes:**
- Code dupliqué dans bot-zoo.js et trade.js

**Correctifs:**
- N/A

**Evolutions:**
- Ajout de `getUpgradeMaxLevels` dans bot-zoo.js
- Ajout de `getSaleListingDefaults` dans trade.js
- Mise à jour de la documentation `centralisations-mutualisations.md`

**Pages affectées:**
- web/js/bot-zoo.js
- web/js/trade.js
- docs/features/centralisations-mutualisations.md

web/js/bot-zoo.js

@@ -15,6 +15,18 @@ import { getEffectiveProfileId, getProfileParams, LEGACY_PROFILE_TO_ID } from ".
 
 const PROFILE_OPTIONS = ["fast", "slow", "balanced"];
 
+/**
+ * Max levels for plot, conveyor/school, and truck from config.
+ * @returns {{ plotMax: number, skillMax: number, truckMax: number }}
+ */
+function getUpgradeMaxLevels() {
+  return {
+    plotMax: GameConfig.Plot?.MaxLevel ?? 8,
+    skillMax: GameConfig.Conveyor?.MaxLevel ?? 8,
+    truckMax: (GameConfig.Truck && GameConfig.Truck.MaxLevel) ?? 5,
+  };
+}
+
 /**
  * @returns {import("./types.js").BotState}
  */
@@ -146,12 +158,10 @@ export function ensureBotState(zoo, isPlayer) {
 function botDecideUpgrade(state, zoo, opts) {
   const { b, rng, params } = opts;
   const { spendThreshold, upgradeChance } = params;
+  const { plotMax, skillMax, truckMax } = getUpgradeMaxLevels();
   const plotCost = getPlotUpgradeCost(b.plotLevel);
-  const plotMax = GameConfig.Plot?.MaxLevel ?? 8;
   const skillCost = getSchoolUpgradeCost(b.conveyorLevel);
-  const skillMax = GameConfig.Conveyor?.MaxLevel ?? 8;
   const truckCost = getTruckUpgradeCost(b.truckLevel);
-  const truckMax = (GameConfig.Truck && GameConfig.Truck.MaxLevel) ?? 5;
   const canUpgradePlot = b.plotLevel < plotMax && b.coins >= plotCost * spendThreshold;
   const canUpgradeSkill = b.conveyorLevel < skillMax && b.coins >= skillCost * spendThreshold;
   const canUpgradeTruck = b.truckLevel < truckMax && b.coins >= truckCost * spendThreshold;
@@ -287,12 +297,10 @@ const PLAYER_AUTO_MAX_INTERVAL = 28;
  */
 function playerAutoDoOneUpgrade(state, params, rng) {
   const { spendThreshold, upgradeChance } = params;
+  const { plotMax, skillMax, truckMax } = getUpgradeMaxLevels();
   const plotCost = getPlotUpgradeCost(state.plotLevel ?? 1);
-  const plotMax = GameConfig.Plot?.MaxLevel ?? 8;
   const skillCost = getConveyorUpgradeCost(state.conveyorLevel ?? 1);
-  const skillMax = GameConfig.Conveyor?.MaxLevel ?? 8;
   const truckCost = getTruckUpgradeCost(state.truckLevel ?? 1);
-  const truckMax = (GameConfig.Truck && GameConfig.Truck.MaxLevel) ?? 5;
   const canPlot = (state.plotLevel ?? 1) < plotMax && state.coins >= plotCost * spendThreshold;
   const canSkill = (state.conveyorLevel ?? 1) < skillMax && state.coins >= skillCost * spendThreshold;
   const canTruck = (state.truckLevel ?? 1) < truckMax && state.coins >= truckCost * spendThreshold;