fix(dashboard): portal modals to .dash-root so they anchor to the viewport

A transformed/overflow panel ancestor was trapping the modal overlay's
position:fixed, so the modal rendered offset inside the messenger/inbox panel
and clipped (Group settings sat inside the thread pane; the compose modal's
top was cut at the panel edge). Portal the overlay up to .dash-root — above
those panels but still inside the scoped design-system CSS — so it centers on
the viewport and the 90vh cap works. Falls back to inline render if no
.dash-root is present.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/components/dashboard/ui.tsx

@@ -14,6 +14,7 @@ import {
   createContext, useCallback, useContext, useEffect, useId,
   useRef, useState, type ReactNode,
 } from "react";
+import { createPortal } from "react-dom";
 import {
   MessageCircle, Ticket, Phone, Mail, BookOpen, Rocket, Shield, ShieldCheck,
   Lock, CreditCard, User, Bell, Eye, EyeOff, Camera, Upload, Plus, Star, Send,
@@ -221,6 +222,11 @@ export function Modal({ open, onClose, title, subtitle, icon, children, footer,
   children: ReactNode; footer?: ReactNode; size?: "sm" | "md" | "lg";
 }) {
   const titleId = useId();
+  // Portal the overlay up to `.dash-root` so its position:fixed anchors to the viewport,
+  // not to a transformed/overflow panel ancestor (which would clip or offset the modal).
+  const [host, setHost] = useState<Element | null>(null);
+  const [mounted, setMounted] = useState(false);
+  useEffect(() => { setHost(document.querySelector(".dash-root")); setMounted(true); }, []);
   useEffect(() => {
     if (!open) return;
     const onKey = (e: KeyboardEvent) => { if (e.key === "Escape") onClose(); };
@@ -228,8 +234,8 @@ export function Modal({ open, onClose, title, subtitle, icon, children, footer,
     return () => document.removeEventListener("keydown", onKey);
   }, [open, onClose]);
 
-  if (!open) return null;
-  return (
+  if (!open || !mounted) return null;
+  const overlay = (
     <div className="ds-modal-overlay" onMouseDown={onClose}>
       <div className={`ds-modal size-${size}`} role="dialog" aria-modal="true" aria-labelledby={titleId} onMouseDown={(e) => e.stopPropagation()}>
         <div className="ds-modal-head">
@@ -247,6 +253,7 @@ export function Modal({ open, onClose, title, subtitle, icon, children, footer,
       </div>
     </div>
   );
+  return host ? createPortal(overlay, host) : overlay;
 }
 
 /* ---------------------------------------------------------- */