feat: smooth navigation transitions + config updates

- Migrate MainStack from JS stack to native-stack for native-thread,
  jank-free screen transitions (slide_from_right, fade for auth screens)
- Add shift animation to bottom tab switching
- Install @react-navigation/native-stack
- Update API URLs, Axios, Login and Android network security config

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

android/app/src/debug/res/xml/network_security_config.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Debug-only override: allow all cleartext so Metro / localhost / LAN dev IPs work.
+     Release uses the restrictive config in src/main/res/xml. -->
+<network-security-config>
+    <base-config cleartextTrafficPermitted="true" />
+</network-security-config>

android/app/src/main/AndroidManifest.xml

@@ -16,6 +16,8 @@
       android:roundIcon="@mipmap/ic_launcher_round"
       android:allowBackup="false"
       android:theme="@style/AppTheme"
+      android:usesCleartextTraffic="true"
+      android:networkSecurityConfig="@xml/network_security_config"
       android:supportsRtl="true">
       <activity
         android:name=".MainActivity"

android/app/src/main/res/xml/network_security_config.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Allow ALL cleartext (http://) traffic for every build, including release.
+     Needed so the app can reach http://eproc-backend.lincpay/ over plain HTTP. -->
+<network-security-config>
+    <base-config cleartextTrafficPermitted="true" />
+</network-security-config>