feat: Phase 3 — services, stores, navigation, design system

Services: ws.service, api.service, simulation.service, rssi.service (android+ios)
Stores: poseStore, settingsStore, matStore (Zustand)
Types: sensing, mat, api, navigation
Hooks: usePoseStream, useRssiScanner, useServerReachability
Theme: colors, typography, spacing, ThemeContext
Navigation: MainTabs (5 tabs), RootNavigator, types
Components: GaugeArc, SparklineChart, OccupancyGrid, StatusDot, ConnectionBanner, SignalBar, +more
Utils: ringBuffer, colorMap, formatters, urlValidator

Verified: tsc 0 errors, jest passes

mobile/src/components/ErrorBoundary.tsx

@@ -0,0 +1,66 @@
+import { Component, ErrorInfo, ReactNode } from 'react';
+import { Button, StyleSheet, View } from 'react-native';
+import { ThemedText } from './ThemedText';
+import { ThemedView } from './ThemedView';
+
+type ErrorBoundaryProps = {
+  children: ReactNode;
+};
+
+type ErrorBoundaryState = {
+  hasError: boolean;
+  error?: Error;
+};
+
+export class ErrorBoundary extends Component<ErrorBoundaryProps, ErrorBoundaryState> {
+  constructor(props: ErrorBoundaryProps) {
+    super(props);
+    this.state = { hasError: false };
+  }
+
+  static getDerivedStateFromError(error: Error): ErrorBoundaryState {
+    return { hasError: true, error };
+  }
+
+  componentDidCatch(error: Error, errorInfo: ErrorInfo) {
+    console.error('ErrorBoundary caught an error', error, errorInfo);
+  }
+
+  handleRetry = () => {
+    this.setState({ hasError: false, error: undefined });
+  };
+
+  render() {
+    if (this.state.hasError) {
+      return (
+        <ThemedView style={styles.container}>
+          <ThemedText preset="displayMd">Something went wrong</ThemedText>
+          <ThemedText preset="bodySm" style={styles.message}>
+            {this.state.error?.message ?? 'An unexpected error occurred.'}
+          </ThemedText>
+          <View style={styles.buttonWrap}>
+            <Button title="Retry" onPress={this.handleRetry} />
+          </View>
+        </ThemedView>
+      );
+    }
+
+    return this.props.children;
+  }
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    justifyContent: 'center',
+    alignItems: 'center',
+    padding: 20,
+    gap: 12,
+  },
+  message: {
+    textAlign: 'center',
+  },
+  buttonWrap: {
+    marginTop: 8,
+  },
+});