feat(ui): add Button, Modal, Spinner, Toast, and Tooltip components with styles

- Implemented Button component with various props for customization.
- Created Modal component with header, content, and footer subcomponents.
- Added Spinner component for loading indicators.
- Developed Toast component for displaying notifications.
- Introduced Tooltip component for contextual hints with keyboard shortcuts.
- Added corresponding CSS modules for styling each component.
- Updated index file to export new components.
- Configured TypeScript settings for the UI package.

packages/shared/src/components/voice/SignalStrengthIcon.tsx

@@ -0,0 +1,20 @@
+import { CellSignalFull, CellSignalMedium, CellSignalLow, CellSignalSlash } from '@phosphor-icons/react';
+import { ConnectionQuality } from 'livekit-client';
+
+interface SignalStrengthIconProps {
+	quality: ConnectionQuality;
+	size?: number;
+}
+
+export function SignalStrengthIcon({ quality, size = 18 }: SignalStrengthIconProps) {
+	if (quality === ConnectionQuality.Excellent) {
+		return <CellSignalFull size={size} weight="bold" color="var(--voice-status-success)" />;
+	}
+	if (quality === ConnectionQuality.Good) {
+		return <CellSignalMedium size={size} weight="bold" color="var(--voice-status-warning)" />;
+	}
+	if (quality === ConnectionQuality.Poor) {
+		return <CellSignalLow size={size} weight="bold" color="var(--voice-status-danger)" />;
+	}
+	return <CellSignalSlash size={size} weight="bold" color="var(--voice-text-subtle)" />;
+}