chore: initialize @limitless/ui git repo + add AppShell

This brings the long-untracked @limitless/ui source tree under version
control. Until now /srv/k8s/templates/limitless-ui has been a plain
file: dependency consumed by gscChronos / gscCRM / gscAdmin, with
copies scattered across web/gsc{Portal,WWW,Aether,Register}/ and
apps/gsc{Meet,Share}/. None were git-tracked.

Treating /srv/k8s/templates/limitless-ui as the canonical going
forward; secondary copies should be replaced with this version
in their consumers' Dockerfiles when they next get touched.

Changes in this initial commit beyond the snapshot:
- Add src/layout/AppShell.tsx — runtime-loaded chrome (header,
  sidebar, footer) backed by gsc-shell-api. Public surface:
    AppShell, ShellProvider, useShell, ShellConfig types
  Framework-agnostic (no Next.js dep). Apps pass appKey + apiUrl +
  getToken; AppShell composes the existing PageShell / Navbar /
  Sidebar / Footer primitives with API data.
- Re-export AppShell from src/index.ts.
- Fix build script: `tsc -p tsconfig.json --noEmit false`. The bare
  `tsc` command was a no-op because tsconfig.json sets noEmit:true
  for typecheck speed. Existing dist/ only existed because of an
  earlier emit; clean rebuilds were silently broken.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/Modal.tsx

@@ -0,0 +1,66 @@
+import React, { useEffect } from 'react';
+import { createPortal } from 'react-dom';
+
+export type ModalProps = {
+  open: boolean;
+  onClose?: () => void;
+  title?: React.ReactNode;
+  size?: 'sm' | 'lg' | 'xl';
+  centered?: boolean;
+  scrollable?: boolean;
+  children: React.ReactNode;
+  footer?: React.ReactNode;
+};
+
+/**
+ * Bootstrap-style modal rendered in a portal with backdrop.
+ */
+export function Modal({ open, onClose, title, size, centered, scrollable, children, footer }: ModalProps) {
+  const modalBody = (
+    <div className={`modal fade ${open ? 'show' : ''}`} style={{ display: open ? 'block' : 'none' }} role="dialog" aria-modal="true">
+      <div
+        className={[
+          'modal-dialog',
+          size ? `modal-${size}` : '',
+          centered ? 'modal-dialog-centered' : '',
+          scrollable ? 'modal-dialog-scrollable' : ''
+        ]
+          .filter(Boolean)
+          .join(' ')}
+      >
+        <div className="modal-content">
+          {title ? (
+            <div className="modal-header">
+              <h5 className="modal-title">{title}</h5>
+              {onClose ? (
+                <button type="button" className="btn-close" aria-label="Close" onClick={onClose}></button>
+              ) : null}
+            </div>
+          ) : null}
+          <div className="modal-body">{children}</div>
+          {footer ? <div className="modal-footer">{footer}</div> : null}
+        </div>
+      </div>
+      <div className={`modal-backdrop fade ${open ? 'show' : ''}`} />
+    </div>
+  );
+
+  useEffect(() => {
+    if (typeof document === 'undefined') return;
+    if (!open) return;
+    const body = document.body;
+    const previousOverflow = body.style.overflow;
+    body.style.overflow = 'hidden';
+    body.classList.add('modal-open');
+    return () => {
+      body.style.overflow = previousOverflow;
+      body.classList.remove('modal-open');
+    };
+  }, [open]);
+
+  if (typeof document === 'undefined') {
+    return null;
+  }
+
+  return createPortal(modalBody, document.body);
+}