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/ModeBadge.tsx

@@ -0,0 +1,71 @@
+import { StyleSheet } from 'react-native';
+import { ThemedText } from './ThemedText';
+import { colors } from '../theme/colors';
+
+type Mode = 'CSI' | 'RSSI' | 'SIM' | 'LIVE';
+
+const modeStyle: Record<
+  Mode,
+  {
+    background: string;
+    border: string;
+    color: string;
+  }
+> = {
+  CSI: {
+    background: 'rgba(50, 184, 198, 0.25)',
+    border: colors.accent,
+    color: colors.accent,
+  },
+  RSSI: {
+    background: 'rgba(255, 165, 2, 0.2)',
+    border: colors.warn,
+    color: colors.warn,
+  },
+  SIM: {
+    background: 'rgba(255, 71, 87, 0.18)',
+    border: colors.simulated,
+    color: colors.simulated,
+  },
+  LIVE: {
+    background: 'rgba(46, 213, 115, 0.18)',
+    border: colors.connected,
+    color: colors.connected,
+  },
+};
+
+type ModeBadgeProps = {
+  mode: Mode;
+};
+
+export const ModeBadge = ({ mode }: ModeBadgeProps) => {
+  const style = modeStyle[mode];
+
+  return (
+    <ThemedText
+      preset="labelMd"
+      style={[
+        styles.badge,
+        {
+          backgroundColor: style.background,
+          borderColor: style.border,
+          color: style.color,
+        },
+      ]}
+    >
+      {mode}
+    </ThemedText>
+  );
+};
+
+const styles = StyleSheet.create({
+  badge: {
+    paddingHorizontal: 10,
+    paddingVertical: 4,
+    borderRadius: 999,
+    borderWidth: 1,
+    overflow: 'hidden',
+    letterSpacing: 1,
+    textAlign: 'center',
+  },
+});