Restructure 7 modal components to use 3-layer architecture preventing
native select dropdown menus from being blocked by modal overlays.
Components fixed:
- ProxyHostForm: ACL selector and Security Headers dropdowns
- User management: Role and permission mode selection
- Uptime monitors: Monitor type selection (HTTP/TCP)
- Remote servers: Provider selection dropdown
- CrowdSec: IP ban duration selection
The fix separates modal background overlay (z-40) from form container
(z-50) and enables pointer events only on form content, allowing
native dropdown menus to render above all modal layers.
Resolves user inability to select security policies, user roles,
monitor types, and other critical configuration options through
the UI interface.
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