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/trade.js

@@ -6,6 +6,17 @@ import { getBlockKeysFromCell } from "./placement.js";
 import { GameConfig } from "./config.js";
 import { getReproductionScore } from "./reproduction.js";
 
+/**
+ * Default duration and price for a new sale listing from config.
+ * @returns {{ duration: number, price: number }}
+ */
+function getSaleListingDefaults() {
+  return {
+    duration: GameConfig.Sale?.ListingDurationSeconds ?? 3600,
+    price: GameConfig.Sale?.DefaultPrice ?? 50,
+  };
+}
+
 /**
  * Put a mature baby from nursery on sale (phase 10). Removes it from pendingBabies and clears the nursery cell.
  * @param {import("./types.js").GameState} state
@@ -27,8 +38,7 @@ export function addMatureBabyToSale(state, nurseryCellKey) {
   const cell = state.grid.cells[nurseryCellKey];
   if (cell && cell.kind === "nursery") cell.tokenId = undefined;
   state.saleListings = state.saleListings ?? [];
-  const duration = GameConfig.Sale?.ListingDurationSeconds ?? 3600;
-  const price = GameConfig.Sale?.DefaultPrice ?? 50;
+  const { duration, price } = getSaleListingDefaults();
   const listingId = `sale_${state.nextTokenId}`;
   state.nextTokenId += 1;
   state.saleListings.push({
@@ -63,8 +73,7 @@ export function addReceptionAnimalToSale(state, receptionCellKey) {
   const rec = receptionAnimals[idx];
   state.receptionAnimals = receptionAnimals.filter((_, i) => i !== idx);
   state.saleListings = state.saleListings ?? [];
-  const duration = GameConfig.Sale?.ListingDurationSeconds ?? 3600;
-  const price = GameConfig.Sale?.DefaultPrice ?? 50;
+  const { duration, price } = getSaleListingDefaults();
   const listingId = `sale_${state.nextTokenId}`;
   state.nextTokenId += 1;
   state.saleListings.push({