refactor(pill-nav): drop Settings entry, guard on settingsHref

Settings lives in the Workbench now — no longer needs its own pill.
settingsHref becomes optional; both places that render the entry
(user-menu link list + nav overflow dropdown) skip it when unset.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -974,7 +974,6 @@
 					currentSyncLabel={syncStatus.label}
 					{appItems}
 					{userEmail}
-					settingsHref="/"
 					manaHref="/mana"
 					profileHref="/profile"
 					spiralHref="/spiral"

packages/shared-ui/src/navigation/PillNavigation.svelte

@@ -379,7 +379,7 @@
 		appItems = [],
 		showAppSwitcher = false,
 		userEmail,
-		settingsHref = '/settings',
+		settingsHref,
 		manaHref,
 		profileHref,
 		loginHref,
@@ -476,13 +476,15 @@
 				active: currentPath === profileHref,
 			});
 		}
-		links.push({
-			id: 'settings',
-			label: 'Einstellungen',
-			icon: 'settings',
-			href: settingsHref,
-			active: currentPath === settingsHref,
-		});
+		if (settingsHref) {
+			links.push({
+				id: 'settings',
+				label: 'Einstellungen',
+				icon: 'settings',
+				href: settingsHref,
+				active: currentPath === settingsHref,
+			});
+		}
 		if (userEmail && manaHref) {
 			links.push({
 				id: 'mana',