fix(manacore): use manaHref for proper Mana icon in user dropdown

Move Mana link from navItems to manaHref prop for consistent display
with the special Mana icon (water drop) in the user dropdown, matching
the Chat app pattern.

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

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

apps/manacore/apps/web/src/routes/(app)/+layout.svelte

@@ -53,7 +53,6 @@
 	// Navigation items for ManaCore
 	const navItems: PillNavItem[] = [
 		{ href: '/dashboard', label: 'Dashboard', icon: 'home' },
-		{ href: '/mana', label: 'Mana', icon: 'fire' },
 		{ href: '/credits', label: 'Credits', icon: 'creditCard' },
 		{ href: '/feedback', label: 'Feedback', icon: 'chat' },
 		{ href: '/profile', label: 'Profil', icon: 'user' },
@@ -175,6 +174,7 @@
 			{appItems}
 			{userEmail}
 			settingsHref="/settings"
+			manaHref="/mana"
 			profileHref="/profile"
 		/>