Initial commit: private Texas Hold'em ring game site (lobby + table stub)

- 6-digit access key gate with long-lived HttpOnly cookie, brute-force limits
- Lobby with saved player name and live table list
- Table creation (name, starting stack, blinds, blind timer)
- Table play screen stub (seats, button/SB/BB, phase, blinds, timer)
- Security hardening: strict CSP, origin checks, host pinning, input sanitizing

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/assets/blinds.js

@@ -0,0 +1,57 @@
+// ブラインド計算（サーバ・ブラウザ共用）
+(function (root, factory) {
+  if (typeof module === 'object' && module.exports) module.exports = factory();
+  else root.Blinds = factory();
+})(typeof self !== 'undefined' ? self : this, function () {
+  'use strict';
+
+  // 1, 2, 3, 4, 5, 6, 10, 15, 20, 25, 30, 40, 50, 60, 75, 100, 150, ...
+  const MANTISSAS = [1, 1.5, 2, 2.5, 3, 4, 5, 6, 7.5];
+  const LADDER = [];
+  for (let e = 0; e <= 9; e++) {
+    for (const m of MANTISSAS) {
+      const v = Math.round(m * Math.pow(10, e) * 100) / 100;
+      if (Number.isInteger(v)) LADDER.push(v);
+    }
+  }
+
+  function nearestNice(x) {
+    if (!(x >= 1)) return 1;
+    let best = LADDER[0];
+    for (const v of LADDER) if (Math.abs(v - x) < Math.abs(best - x)) best = v;
+    return best;
+  }
+
+  // 開始スタックに合うブラインド（BB = スタックの約1/100）
+  function defaultBlinds(stack) {
+    const sb = nearestNice(stack / 200);
+    return { sb, bb: sb * 2 };
+  }
+
+  // 1レベルごとに約1.5倍
+  function nextSmallBlind(sb) {
+    const target = sb * 1.4;
+    for (const v of LADDER) if (v >= target && v > sb) return v;
+    return Math.ceil(sb * 1.5);
+  }
+
+  // level は 1 始まり
+  function blindsAt(sb0, bb0, level) {
+    const ratio = bb0 / sb0;
+    let sb = sb0;
+    let bb = bb0;
+    for (let i = 2; i <= level; i++) {
+      sb = nextSmallBlind(sb);
+      bb = Math.round(sb * ratio);
+    }
+    return { sb, bb };
+  }
+
+  function schedule(sb0, bb0, levels) {
+    const out = [];
+    for (let i = 1; i <= levels; i++) out.push(Object.assign({ level: i }, blindsAt(sb0, bb0, i)));
+    return out;
+  }
+
+  return { defaultBlinds, blindsAt, schedule };
+});