feat(assets): add TypeScript type declarations for Hugo @params module

Add proper type definitions for Hugo's `@params` virtual module, configure
tsconfig paths/typeRoots for resolution, and remove the @ts-expect-error
suppress in color-scheme.ts. Also fix nil input handling in camel-case-keys.

layouts/_partials/function/camel-case-keys.html

@@ -26,7 +26,7 @@
   // Practical usage in templates
   {{- $siteParams := partial "function/camel-case-keys.html" .Site.Params }}
 */ -}}
-{{- $input := . -}}
+{{- $input := . | default dict -}}
 {{- $output := dict -}}
 
 {{- if reflect.IsMap $input -}}