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/utils/formatters.ts

@@ -0,0 +1,34 @@
+export function formatRssi(v: number | null | undefined): string {
+  if (typeof v !== 'number' || !Number.isFinite(v)) {
+    return '-- dBm';
+  }
+  return `${Math.round(v)} dBm`;
+}
+
+export function formatBpm(v: number | null | undefined): string {
+  if (typeof v !== 'number' || !Number.isFinite(v)) {
+    return '--';
+  }
+  return `${Math.round(v)} BPM`;
+}
+
+export function formatConfidence(v: number | null | undefined): string {
+  if (typeof v !== 'number' || !Number.isFinite(v)) {
+    return '--';
+  }
+  const normalized = v > 1 ? v / 100 : v;
+  return `${Math.round(Math.max(0, Math.min(1, normalized)) * 100)}%`;
+}
+
+export function formatUptime(ms: number | null | undefined): string {
+  if (typeof ms !== 'number' || !Number.isFinite(ms) || ms < 0) {
+    return '--:--:--';
+  }
+
+  const totalSeconds = Math.floor(ms / 1000);
+  const hours = Math.floor(totalSeconds / 3600);
+  const minutes = Math.floor((totalSeconds % 3600) / 60);
+  const seconds = totalSeconds % 60;
+
+  return `${String(hours).padStart(2, '0')}:${String(minutes).padStart(2, '0')}:${String(seconds).padStart(2, '0')}`;
+}