Add turn timer functionality to Table class; update environment configuration

.env.example

@@ -20,3 +20,4 @@ MIN_BET=10
 MAX_BET=500
 ROUND_START_DELAY_MS=3000
 ROUND_RESET_DELAY_MS=5000
+TURN_TIME_MS=15000

src/game/tables.js

@@ -5,6 +5,7 @@ const MIN_BET = Number(process.env.MIN_BET || 10);
 const MAX_BET = Number(process.env.MAX_BET || 100);
 const ROUND_START_DELAY_MS = Number(process.env.ROUND_START_DELAY_MS || 3000);
 const ROUND_RESET_DELAY_MS = Number(process.env.ROUND_RESET_DELAY_MS || 5000);
+const TURN_TIME_MS = Number(process.env.TURN_TIME_MS || 15000);
 
 class Table {
   constructor(id, seatCount) {
@@ -26,6 +27,9 @@ class Table {
     this.roundId = 0;
     this.roundTimeout = null;
     this.resetTimeout = null;
+    this.turnTimeout = null;
+    this.turnEndsAt = null;
+    this.turnCounter = 0;
     this.clients = new Set();
   }
 
@@ -55,6 +59,7 @@ class Table {
       minBet: MIN_BET,
       maxBet: MAX_BET,
       roundId: this.roundId,
+      turnEndsAt: this.turnEndsAt,
       dealerHand,
       currentSeatIndex: this.currentSeatIndex,
       seats: this.seats.map((seat, index) => ({
@@ -103,6 +108,36 @@ class Table {
     }
   }
 
+  clearTurnTimer() {
+    if (this.turnTimeout) {
+      clearTimeout(this.turnTimeout);
+    }
+    this.turnTimeout = null;
+    this.turnEndsAt = null;
+  }
+
+  startTurnTimer() {
+    this.clearTurnTimer();
+    if (this.currentSeatIndex === null) {
+      return;
+    }
+
+    this.turnEndsAt = Date.now() + TURN_TIME_MS;
+    const turnToken = ++this.turnCounter;
+
+    this.turnTimeout = setTimeout(() => {
+      if (this.turnCounter !== turnToken) {
+        return;
+      }
+      const seat = this.seats[this.currentSeatIndex];
+      if (!seat || seat.status !== 'playing') {
+        return;
+      }
+      seat.status = 'stood';
+      void this.advanceTurn();
+    }, TURN_TIME_MS);
+  }
+
   findSeatIndexByUser(userId) {
     return this.seats.findIndex((seat) => seat.userId === userId);
   }
@@ -251,6 +286,7 @@ class Table {
       return;
     }
 
+    this.clearTurnTimer();
     this.phase = 'playing';
     this.roundId += 1;
     this.deck = shuffle(createDeck());
@@ -272,6 +308,7 @@ class Table {
       return;
     }
 
+    this.startTurnTimer();
     this.broadcastState();
   }
 
@@ -310,6 +347,8 @@ class Table {
       } else if (value === 21) {
         seat.status = 'stood';
         await this.advanceTurn();
+      } else {
+        this.startTurnTimer();
       }
     } else if (action === 'stand') {
       seat.status = 'stood';
@@ -343,15 +382,18 @@ class Table {
   async advanceTurn() {
     const nextIndex = this.nextPlayableSeatIndex(this.currentSeatIndex ?? -1);
     if (nextIndex === null) {
+      this.clearTurnTimer();
       await this.dealerTurn();
       return;
     }
 
     this.currentSeatIndex = nextIndex;
+    this.startTurnTimer();
     this.broadcastState();
   }
 
   async dealerTurn() {
+    this.clearTurnTimer();
     this.phase = 'dealer';
     this.currentSeatIndex = null;
 
@@ -423,6 +465,7 @@ class Table {
   }
 
   resetRound() {
+    this.clearTurnTimer();
     for (const seat of this.seats) {
       if (!seat.userId) {
         continue;