Fix: Support dynamic locale switching (Fixes #85)

[robotex82]

Fix: Support dynamic locale switching (Fixes #85)

Description

This PR fixes an issue where documentation content and the sidebar would stick to the boot-time locale (typically from .env), ignoring runtime locale changes (e.g., via middleware).

Changes

1. Multi-Locale Loading: Updated FlatfileNode::getRows() to scan and load documentation for all available locales found in the docs directory, rather than just the current app locale.
   • Records are now namespaced by locale (e.g., de.welcome) to prevent ID collisions in the Sushi cache.
   • Added a locale column to the FlatfileNode schema.
2. Strict Filtering: Added a Global Scope to FlatfileNode that filters all queries by App::getLocale().
   • This ensures that FlatfileNode::all(), used by the sidebar navigation builder, only returns items for the current user's language.
   • This prevents "sidebar leakage" where English items would appear for German users if navigation was built before the locale switch.
3. Route Binding: Updated resolveRouteBindingQuery to scope lookups to the current locale.

Verification

Verified that switching the user's locale at runtime correctly updates both the documentation content and the sidebar navigation structure.