feat(monopoly): add sound effects for payment and pawn animations

- Play sfx-monopoly-pay when rent/payment animation begins
- Play sfx-piece-click when pawn/token hop animation completes
- Load new audio asset and register in SFX constants

public/src/games/monopoly/MonopolyGame.js

@@ -708,21 +708,56 @@ export default class MonopolyGame extends Phaser.Scene {
     if (!isHumanTurn && !auctionIsHuman) return;
     if (inAuction) return; // auction panel handles its own buttons
 
-    const btnY0 = this.diceY + 56;
     const btnW  = RP_W - 20;
+    const BTN_H = 52;
+    const BTN_GAP = 10; // spacing between buttons (62 = BTN_H + BTN_GAP)
+
+    // First pass: count buttons to determine starting Y
+    const p = gs.players[this.humanSeat];
+    const phase = gs.phase;
+    let btnCount = 0;
+
+    if (phase === 'preroll' || phase === 'endturn') {
+      if (phase === 'preroll') {
+        if (p.jailed) {
+          if (p.getOutOfJailFree > 0) btnCount++;
+          btnCount++;
+          btnCount++;
+        } else {
+          btnCount++;
+        }
+      }
+      if (phase === 'endturn') btnCount++;
+      if (PURCHASABLE.some(idx =>
+        canBuildHouse(gs, this.humanSeat, idx) || canBuildHotel(gs, this.humanSeat, idx))) {
+        btnCount++;
+      }
+      if (PURCHASABLE.some(idx => {
+        const own = gs.board[idx];
+        return own?.owner === this.humanSeat && !own.mortgaged && own.houses === 0 && !own.hotel;
+      }) || PURCHASABLE.some(idx => {
+        const own = gs.board[idx];
+        return own?.owner === this.humanSeat && own.mortgaged &&
+          p.cash >= Math.ceil(SPACES[idx].mortgage * 1.1);
+      })) {
+        btnCount++;
+      }
+    }
+
+    // Second pass: draw buttons aligned to board bottom (BT + BS)
+    const boardBottom = BT + BS;
+    const totalBtnH = btnCount * BTN_H + (btnCount - 1) * BTN_GAP;
+    const btnY0 = boardBottom - totalBtnH;
     let yOff = 0;
     const mkBtn = (label, cb, enabled=true, opts={}) => {
       const btn = new Button(this, RP_X + btnW/2 + 10, btnY0 + yOff, label, cb,
-        { width: btnW, height: 52, fontSize: 22, ...opts });
+        { width: btnW, height: BTN_H, fontSize: 22, ...opts });
       btn.setDepth(DEPTH.ui);
       if (!enabled) btn.setEnabled(false);
       this.reg(btn);
-      yOff += 62;
+      yOff += BTN_H + BTN_GAP;
     };
 
-    const p = gs.players[this.humanSeat];
-    const phase = gs.phase;
-
     if (phase === 'preroll' || phase === 'endturn') {
       if (phase === 'preroll') {
         if (p.jailed) {
@@ -810,6 +845,8 @@ export default class MonopolyGame extends Phaser.Scene {
 
     await this.delay(250);
 
+    playSound(this, SFX.MONOPAY);
+
     // Phase 3: Amount arches to receiver's panel (1200 ms), turns green, adds plus
     amtTxt.setText(`+$${amount.toLocaleString()}`);
     amtTxt.setColor('#44FF88');
@@ -1478,8 +1515,8 @@ export default class MonopolyGame extends Phaser.Scene {
   async executeRoll(seat) {
     const d1 = Math.floor(Math.random() * 6) + 1;
     const d2 = Math.floor(Math.random() * 6) + 1;
+    playSound(this, SFX.DICE_ROLL);
     await this.animateDice(d1, d2);
-    playSound(this, SFX.diceRoll);
     const prevPos = this.gs.players[seat].position;
     const wasJailed = this.gs.players[seat].jailed;
     this.gs = rollDice(this.gs, seat, d1, d2);
@@ -1572,7 +1609,10 @@ export default class MonopolyGame extends Phaser.Scene {
             pawn.x = inv * inv * start.x + 2 * inv * t * ctrl.x + t * t * ex;
             pawn.y = inv * inv * start.y + 2 * inv * t * ctrl.y + t * t * ey;
           },
-          onComplete: hopOne,
+          onComplete: () => {
+            playSound(this, SFX.PIECE_CLICK);
+            hopOne();
+          },
         });
       };
 

public/src/scenes/PreloadScene.js

@@ -138,6 +138,7 @@ export default class PreloadScene extends Phaser.Scene {
     this.load.spritesheet('monopoly-cards', '/assets/images/monopoly-cards.png', { frameWidth: 200, frameHeight: 300 });
     this.load.audio('sfx-monopoly-purchase', '/assets/fx/monopoly-purchase.mp3');
     this.load.audio('sfx-monopoly-expense',  '/assets/fx/monopoly-expense.mp3');
+    this.load.audio('sfx-monopoly-pay',      '/assets/fx/monopoly-pay.mp3');
     this.load.audio('sfx-monopoly-paid',     '/assets/fx/monopoly-paid.mp3');
   }
 

public/src/ui/Sounds.js

@@ -34,6 +34,7 @@ export const SFX = {
   SCIFI_WOOSH:           'sfx-scifi-woosh',
   MONOPOLY_PURCHASE:     'sfx-monopoly-purchase',
   MONOPOLY_EXPENSE:      'sfx-monopoly-expense',
+  MONOPAY:               'sfx-monopoly-pay',
   MONOPOLY_PAID:         'sfx-monopoly-paid',
 };