Block pinch and double-tap zoom, including on iOS Safari

iOS Safari ignores user-scalable=no, so zoom is blocked in three layers:
- viewport meta: maximum-scale=1, user-scalable=no on every page
  (covers Android, home-screen apps and iOS focus zoom on inputs)
- CSS: touch-action: pan-x pan-y on html, so scrolling still works but
  pinch and double-tap zoom do not
- JS (fluid.js): cancel Safari's gesture* events and two-finger touchmove

Double-tap is left to CSS rather than JS so rapid repeated taps on
buttons still register as clicks.

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

public/assets/style.css

@@ -173,6 +173,8 @@ html {
   -webkit-text-size-adjust: 100%;
   text-size-adjust: 100%;
   background: var(--bg);
+  /* スクロールだけ許し、ピンチとダブルタップの拡大は止める（子の touch-action もこれに絞られる） */
+  touch-action: pan-x pan-y;
 }
 
 body {
@@ -1462,7 +1464,7 @@ body.page-table {
   display: flex;
   flex-direction: column;
   background: var(--room);
-  touch-action: manipulation; /* ダブルタップでの拡大を防ぐ（ピンチ拡大は残す） */
+  touch-action: pan-x pan-y; /* ダブルタップ・ピンチでの拡大を防ぐ */
   -webkit-user-select: none;
   user-select: none;
   -webkit-touch-callout: none;