fix: align NavigationItem and NavigationArea label types with @objectstack/spec v4

Updated NavigationItem.label and NavigationArea.label to use plain string type instead of the legacy i18n object format `{key, defaultValue}`.

This aligns our type definitions with @objectstack/spec v4 protocol which requires label fields to be plain strings only.

Note: The validation warning from @objectstack/plugin-auth persists because that package's runtime code still transforms string labels into i18n objects. This is an upstream issue in the @objectstack framework.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Claude

packages/types/src/app.ts

@@ -55,8 +55,8 @@ export interface NavigationItem {
   /** Navigation item type */
   type: NavigationItemType;
 
-  /** Display label (plain string or I18nLabel object for internationalization) */
-  label: string | { key: string; defaultValue?: string; params?: Record<string, any> };
+  /** Display label (plain string per @objectstack/spec v4 protocol) */
+  label: string;
 
   /** Icon name (Lucide) */
   icon?: string;
@@ -129,8 +129,8 @@ export interface NavigationArea {
   /** Unique identifier */
   id: string;
 
-  /** Display label (plain string or I18nLabel object for internationalization) */
-  label: string | { key: string; defaultValue?: string; params?: Record<string, any> };
+  /** Display label (plain string per @objectstack/spec v4 protocol) */
+  label: string;
 
   /** Icon name (Lucide) */
   icon?: string;