Task #703: تمكين التمرير داخل نافذة الحجز الطويلة

- DialogShell (artifacts/tx-os/src/pages/protocol.tsx) now caps the dialog at
  max-h-[85vh] with a flex column layout: the title (DialogHeader) and the
  save/cancel footer stay always visible, while the form fields scroll in an
  inner overflow-y-auto area (overscroll-contain).
- Applies to all DialogShell users (booking, room, gift dialogs); short forms
  are unaffected since the container only scrolls when content exceeds 85vh.
- RTL unaffected (dir attribute preserved).
- Verified: tsc clean for tx-os; architect review run.
- Architect flagged a potential grid-vs-flex display conflict in DialogContent,
  but cn() uses tailwind-merge, so the later "flex" class deterministically
  replaces the base "grid" — no change needed.

artifacts/tx-os/src/pages/protocol.tsx

@@ -2533,19 +2533,26 @@ function DialogShell({
   const { i18n, t } = useTranslation();
   return (
     <Dialog open onOpenChange={(o) => !o && onClose()}>
-      <DialogContent dir={i18n.language === "ar" ? "rtl" : "ltr"}>
-        <DialogHeader>
+      <DialogContent
+        dir={i18n.language === "ar" ? "rtl" : "ltr"}
+        className="flex max-h-[85vh] flex-col overflow-hidden"
+      >
+        <DialogHeader className="shrink-0">
           <DialogTitle>{title}</DialogTitle>
         </DialogHeader>
         <form
-          className="space-y-3"
+          className="flex min-h-0 flex-1 flex-col"
           onSubmit={(e) => {
             e.preventDefault();
             onSubmit();
           }}
         >
-          {children}
-          <DialogFooter>
+          {/* Long forms (e.g. the booking form) scroll here while the
+              title and the save/cancel buttons stay visible. */}
+          <div className="min-h-0 flex-1 space-y-3 overflow-y-auto overscroll-contain px-1 py-1 -mx-1">
+            {children}
+          </div>
+          <DialogFooter className="shrink-0 pt-3">
             <Button type="button" variant="ghost" onClick={onClose}>
               {t("common.cancel")}
             </Button>