New navigation model (#1)

* Flatten all routing into a single stack

* Replace router with custom implementation

* Add shell header and titles

* Add tab selector

* Add back/forward history menus on longpress

* Fix: don't modify state during render

* Add refresh() to navigation and reroute navigations to the current location to refresh instead of add to history

* Cache screens during navigation to maintain scroll position and improve load-time for renders

src/view/screens/Login.tsx

@@ -0,0 +1,27 @@
+import React from 'react'
+import {Text, View} from 'react-native'
+import {observer} from 'mobx-react-lite'
+// import {useStores} from '../../state'
+
+export const Login = observer(
+  (/*{navigation}: RootTabsScreenProps<'Login'>*/) => {
+    // const store = useStores()
+    return (
+      <View style={{justifyContent: 'center', alignItems: 'center'}}>
+        <Text style={{fontSize: 20, fontWeight: 'bold'}}>Sign In</Text>
+        {/*store.session.uiError && <Text>{store.session.uiError}</Text>}
+        {!store.session.uiIsProcessing ? (
+          <>
+            <Button title="Login" onPress={() => store.session.login()} />
+            <Button
+              title="Sign Up"
+              onPress={() => navigation.navigate('Signup')}
+            />
+          </>
+        ) : (
+          <ActivityIndicator />
+        )*/}
+      </View>
+    )
+  },
+)