✨ feat(chat): add model comparison feature

Add /compare route to test prompts against multiple Ollama models:
- CompareInput: prompt textarea with temperature/max tokens controls
- ModelResponseCard: displays response with status, metrics, markdown
- ModelResponseGrid: responsive grid layout for side-by-side comparison
- CompareProgress: progress bar with cancel functionality
- Svelte 5 runes-based store for state management
- Add Scales icon to shared-ui navigation

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

@@ -53,6 +53,7 @@
 		CreditCard,
 		Buildings,
 		User,
+		Scales,
 	} from '@manacore/shared-icons';
 
 	// Map icon names to Phosphor components
@@ -103,6 +104,7 @@
 		palette: Palette,
 		creditCard: CreditCard,
 		building: Buildings,
+		scale: Scales,
 	};
 
 	// Convert app items to dropdown items (will be computed as derived)