fix(mobile): type auth selectors and token placeholders

mobile/src/app/auth.tsx

@@ -1,14 +1,14 @@
 import { useState } from 'react';
 import { Pressable, StyleSheet, Text, TextInput, View } from 'react-native';
 import { router } from 'expo-router';
-import { useAuthStore } from '../store/auth-store';
+import { useAuthStore, type AuthState } from '../store/auth-store';
 import { colors } from '../theme';
 
 export default function AuthScreen() {
   const [email, setEmail] = useState('');
   const [password, setPassword] = useState('');
-  const signIn = useAuthStore((state) => state.signIn);
+  const signIn = useAuthStore((state: AuthState) => state.signIn);
-  const isLoading = useAuthStore((state) => state.isLoading);
+  const isLoading = useAuthStore((state: AuthState) => state.isLoading);
 
   return (
     <View style={styles.container}>
@@ -19,14 +19,14 @@ export default function AuthScreen() {
         keyboardType="email-address"
         onChangeText={setEmail}
         placeholder="Email"
-        placeholderTextColor="#7c8698"
+        placeholderTextColor={colors.textTertiary}
         style={styles.input}
         value={email}
       />
       <TextInput
         onChangeText={setPassword}
         placeholder="Password"
-        placeholderTextColor="#7c8698"
+        placeholderTextColor={colors.textTertiary}
         secureTextEntry
         style={styles.input}
         value={password}