Fix Live Activity lock screen rendering and polish multi-account auth.

Flatten widget layouts and use system colors so banner and expanded regions render on vibrant lock screens; migrate auth sessions per account to prevent double sign-in; scope app lock PIN to accounts; default clock description to "Clock In"; add architecture docs and deferred form validation on auth screens.

Co-authored-by: Cursor <cursoragent@cursor.com>

components/ui/Input.tsx

@@ -12,14 +12,18 @@ import { fonts, radii, spacing } from "@/constants/theme";
 type InputProps = TextInputProps & {
   label: string;
   error?: string;
+  required?: boolean;
 };
 
-export function Input({ label, error, style, ...props }: InputProps) {
+export function Input({ label, error, required, style, ...props }: InputProps) {
   const { colors } = useAppTheme();
 
   return (
     <View style={styles.wrapper}>
-      <Text style={[styles.label, { color: colors.foreground }]}>{label}</Text>
+      <Text style={[styles.label, { color: colors.foreground }]}>
+        {label}
+        {required ? <Text style={{ color: colors.destructive }}> *</Text> : null}
+      </Text>
       <TextInput
         placeholderTextColor={colors.mutedForeground}
         style={[