Add layout designer and welcome page templates with embed support

- Introduced a new layout designer page template that supports an embeddable mode for integration within iframes in external applications. This includes hiding CMS navigation and sending postMessage events to the parent window.
- Added a new welcome page template that serves as an onboarding guide for users, featuring step-by-step instructions for connecting displays, uploading content, designing layouts, and scheduling content.
- Included CSS styles for both templates to enhance the user interface and experience.
- Implemented JavaScript functionality for live statistics on the welcome page, fetching counts for displays, media files, layouts, and schedules.

.github/copilot-instructions.md

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+# OTS Signs Theme — Copilot Instructions
+
+Custom Xibo CMS theme for OTS Signs digital signage service. Built with Twig templates, vanilla CSS, and vanilla JS. No build pipeline — all assets are inlined at runtime.
+
+## Architecture
+
+- **Template engine**: Twig, inheriting from Xibo core's `base.twig`
+- **Entry point**: `ots-signs/views/authed.twig` — wraps all authenticated pages (sidebar + topbar + content)
+- **CSS delivery**: CSS files are **inlined** inside `<style nonce="...">` tags via `theme-javascript.twig`, not served as static files. This is intentional — it avoids MIME routing issues under the `custom/` path and ensures CSP nonce compliance.
+- **JS delivery**: Same inline strategy via `theme-scripts.twig`
+- **Config**: `ots-signs/config.php` — sets theme name, URLs, feature flags
+
+### Twig inheritance
+```
+base.twig (Xibo core)
+  ├── authed.twig           ← most pages extend this
+  │   ├── dashboard-icon-page.twig
+  │   ├── layout-page.twig
+  │   └── [40+ admin page templates]
+  └── login.twig
+```
+
+Partials included in `authed.twig`: `authed-sidebar.twig`, `authed-topbar.twig`, `authed-user-menu.twig`, `authed-notification-drawer.twig`
+
+## Key Xibo Template APIs
+
+These are available in all authenticated Twig templates:
+
+```twig
+{# Permission-gated rendering #}
+{% if currentUser.featureEnabled("layout.view") %}...{% endif %}
+
+{# User preferences #}
+{% set navPos = currentUser.getOptionValue("navigationMenuPosition", "vertical") %}
+
+{# Theme helpers #}
+{{ theme.uri("css/override.css") }}
+{{ theme.getSetting("DEFAULT_VALUE", fallback) }}
+{{ url_for("routeName") }}
+{{ trans("string") }}
+```
+
+## CSS Architecture
+
+Primary file: `ots-signs/css/override.css`
+
+- Primary color: `#e87800` (orange), exposed as `--primary-color`
+- Dark background: `#0f172a`, surface: `#1e293b`
+- Sidebar: 256px expanded / 64px collapsed (icon-only), controlled via CSS vars
+- `override-dark.css` handles component-level dark mode, floating menus, DataTable contrast
+
+Do **not** add a build step (Sass, PostCSS, etc.) without first discussing it — the inline delivery mechanism requires plain CSS.
+
+## JS Conventions
+
+Single file: `ots-signs/js/theme.js` (440+ lines)
+
+- IIFE pattern — no module bundler
+- Uses `localStorage` for theme (`ots-theme`) and sidebar state (`ots-sidebar-collapsed`)
+- MutationObserver watches for Xibo's layout editor modal, sets `body.ots-playlist-editor-active`
+- Mobile breakpoint: `768px`
+
+## Deployment
+
+Theme lives at: `web/theme/custom/otssigns-beta/` inside the Xibo CMS installation.
+The `view_path` in `config.php` must point to the absolute path of the `views/` directory.
+
+## Common UI Patterns
+
+| Pattern | Key class/element |
+|---------|------------------|
+| Icon dashboard cards | `.icon-dash-card` with `--blue`, `--green`, `--purple`, `--teal` color vars |
+| Data grids | `.XiboGrid` wrapper → DataTables (managed by Xibo core) |
+| Filter panels | `.XiboFilter` with tab-based advanced filter |
+| Page header | `.page-header` with `<h1>` + subtitle |
+| Toast/alerts | Bootstrap `.alert-danger/warning/success/info` |
+| Forms | `inline.*()` macro system from Xibo core |
+
+## What This Repo Does NOT Have
+
+- No `package.json`, no npm/yarn/pnpm
+- No webpack, Vite, Gulp, or Parcel
+- No TypeScript — plain JS only
+- No PHP unit tests in this repo (Xibo core testing is separate)
+- No CI/CD config
+
+Don't suggest adding any of the above unless the user explicitly asks.