Fix deck border alignment with plank edges

- Calculate deck edges accounting for plank height
- Border now aligns with top of first plank and bottom of last plank
- Proper vertical centering of border rectangle

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/scenes/ShipDeckScene.js

@@ -59,8 +59,13 @@ export default class ShipDeckScene extends Phaser.Scene {
         }
 
         // Draw border around deck
-        const deckHeight = this.deckBottomY - this.deckTopY + 25; // +25 for last plank height
-        const deckBorder = this.add.rectangle(this.deckCenterX, this.deckTopY + (deckHeight / 2), this.deckWidth, deckHeight);
+        const plankHeight = 25;
+        const deckTopEdge = this.deckTopY - (plankHeight / 2);
+        const deckBottomEdge = this.deckBottomY + (plankHeight / 2);
+        const deckHeight = deckBottomEdge - deckTopEdge;
+        const deckCenterY = (deckTopEdge + deckBottomEdge) / 2;
+
+        const deckBorder = this.add.rectangle(this.deckCenterX, deckCenterY, this.deckWidth, deckHeight);
         deckBorder.setStrokeStyle(4, 0x3d2817);
         deckBorder.setFillStyle(0x000000, 0); // Transparent fill
     }