Expo app: native front end for health.rehbock.xyz

Login (HTTP Basic, token in SecureStore) + Today, Blood, Sleep, Train,
Body, Mind, DNA screens ported from the PWA at /app/. All data is
fetched live from health.rehbock.xyz; nothing is stored on device
beyond the auth token.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

package.json

@@ -12,6 +12,7 @@
     "expo-image": "~57.0.2",
     "expo-linking": "~57.0.5",
     "expo-router": "~57.0.11",
+    "expo-secure-store": "~57.0.1",
     "expo-splash-screen": "~57.0.5",
     "expo-status-bar": "~57.0.1",
     "expo-symbols": "~57.0.2",
@@ -24,6 +25,7 @@
     "react-native-reanimated": "4.5.1",
     "react-native-safe-area-context": "~5.7.0",
     "react-native-screens": "~4.26.0",
+    "react-native-svg": "15.15.4",
     "react-native-web": "~0.21.0",
     "react-native-worklets": "0.10.1"
   },