Fix custom routes in Lazy Admin layout

[CrazyBoy49z]

Fixes Undefined variable $routes when a host view passes custom routes to <x-lazy-layout>, including Step2Dev article editing.

Root cause:

• layout.blade.php used $routes but did not declare it in @props;
• Blade therefore treated a passed routes value as a normal attribute and unset the existing $routes variable during @props compilation;
• BaseLayout also did not accept route overrides in its constructor.

Changes:

• declare routes as a layout prop;
• accept optional route overrides in BaseLayout;
• merge overrides with generated defaults so partial overrides such as only show keep create/edit/destroy keys intact;
• add regression coverage for the custom route path used by article editing.