Unified configurable asset path/prefix for sub-folder deployments (SPA on root)

[lmalma]

Currently, deploying a Filament panel on a sub-path (e.g., example.com/app) alongside a frontend SPA (like Vue.js) on the root domain (example.com/) is extremely difficult to configure at the Nginx/web-server level.

The Problem:
My architecture is as follows:

• The root domain / serves a static Vue.js frontend application.
• The sub-path /app serves the Filament PHP panel.

The issue arises with asset routing. Vue expects its assets at the root, but Filament and Livewire also request assets from root-relative paths by default (e.g., /livewire/livewire.js or /filament/assets/...).
Configuring Nginx to correctly route / to Vue, while intercepting specific asset paths for Filament and Livewire and routing them to Laravel's index.php, is highly complex and error-prone.

While it is possible to manually tweak Laravel's ASSET_URL and use Livewire::setScriptRoute(), it feels like there should be a native, streamlined way within Filament to handle this, as sub-folder deployments are a common use case.

Proposed Solution:
Introduce a configuration method in the PanelProvider that allows setting a unified global asset prefix for the specific panel.

For example:

public function panel(Panel $panel): Panel
{
    return $panel
        ->default()
        ->id('app')
        ->path('app')
        ->assetPrefix('/app-assets'); // <-- New feature
}

Behind the scenes, this method would:

1. Ensure all Filament core CSS/JS assets are requested with this prefix.
2. Automatically configure Livewire's update and script routes (Livewire::setScriptRoute / Livewire::setUpdateRoute) to use this prefix.

This would allow developers to easily configure Nginx with a single location ^~ /app-assets/ block that routes directly to Laravel, leaving the rest of the root domain cleanly handled by the SPA frontend.