feat: add upgrade scrolls

src/rendering/ItemSpriteFactory.ts

@@ -36,6 +36,12 @@ export class ItemSpriteFactory {
     sprite.setScale(scale);
     container.add(sprite);
     
+    // Add upgrade level badge if item has been upgraded
+    if (item.upgradeLevel && item.upgradeLevel > 0) {
+      const badge = this.createUpgradeBadge(scene, item.upgradeLevel, scale);
+      container.add(badge);
+    }
+    
     return container;
   }
   
@@ -109,6 +115,31 @@ export class ItemSpriteFactory {
     return variant?.glowColor ?? null;
   }
   
+  /**
+   * Creates a badge displaying the upgrade level (e.g., "+1").
+   */
+  private static createUpgradeBadge(
+    scene: Phaser.Scene,
+    level: number,
+    scale: number
+  ): Phaser.GameObjects.Text {
+    // Position at top-right corner, slightly inset
+    const offset = 5 * scale;
+    
+    // Level text with strong outline for readability without background
+    const text = scene.add.text(offset, -offset, `+${level}`, {
+      fontSize: `${9 * scale}px`,
+      color: "#ffd700",
+      fontStyle: "bold",
+      fontFamily: "monospace",
+      stroke: "#000000",
+      strokeThickness: 3
+    });
+    text.setOrigin(0.5);
+    
+    return text;
+  }
+
   /**
    * Checks if an item has a variant with a glow.
    */