refactor: use CustomTextInput in login and register screens

- Replace raw TextInput with CustomTextInput in login and register
  for consistent focus border effect across the app
- Add placeholder, secureTextEntry, autoCapitalize, keyboardType
  props to CustomTextInput
- Remove hardcoded default padding (px-3 py-2) and h-11/12 from
  CustomTextInput, callers now set padding via className
- Add explicit px-3 py-2 to existing callers (settings, editEvent)
- Update CLAUDE.md with new CustomTextInput usage and props

apps/client/src/app/register.tsx

@@ -1,8 +1,9 @@
 import { useState } from "react";
-import { View, Text, TextInput, Pressable } from "react-native";
+import { View, Text, Pressable } from "react-native";
 import { Link, router } from "expo-router";
 import BaseBackground from "../components/BaseBackground";
 import AuthButton from "../components/AuthButton";
+import CustomTextInput from "../components/CustomTextInput";
 import { AuthService } from "../services";
 import { useThemeStore } from "../stores/ThemeStore";
 
@@ -59,50 +60,32 @@ const RegisterScreen = () => {
           </Text>
         )}
 
-        <TextInput
+        <CustomTextInput
           placeholder="E-Mail"
           placeholderTextColor={theme.textMuted}
-          value={email}
-          onChangeText={setEmail}
+          text={email}
+          onValueChange={setEmail}
           autoCapitalize="none"
           keyboardType="email-address"
           className="w-full rounded-lg p-4 mb-4"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
-        <TextInput
+        <CustomTextInput
           placeholder="Benutzername"
           placeholderTextColor={theme.textMuted}
-          value={userName}
-          onChangeText={setUserName}
+          text={userName}
+          onValueChange={setUserName}
           autoCapitalize="none"
           className="w-full rounded-lg p-4 mb-4"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
-        <TextInput
+        <CustomTextInput
           placeholder="Passwort"
           placeholderTextColor={theme.textMuted}
-          value={password}
-          onChangeText={setPassword}
+          text={password}
+          onValueChange={setPassword}
           secureTextEntry
           className="w-full rounded-lg p-4 mb-6"
-          style={{
-            backgroundColor: theme.secondaryBg,
-            color: theme.textPrimary,
-            borderWidth: 1,
-            borderColor: theme.borderPrimary,
-          }}
         />
 
         <AuthButton