Make RN components fully theme-driven for multi-brand support

Refactor all 18 React Native components from static DTColors imports to
dynamic useDTTheme() context, enabling proper visual differentiation
when switching between DT and Classic brands.

Key changes:
- Replace static DTColors with theme context in all components
- Add shape tokens (bevel/radius) to DTExtendedTheme interface
- Conditionally render SVG bevels (DT) vs borderRadius (Classic)
- Configure fonts per brand (Tektur for DT, system sans-serif for Classic)
- Update buildThemeFromBrand to parse shape and typography tokens
- Fix Metro config for monorepo singleton resolution

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/react-native/src/components/DTModal.tsx

@@ -11,7 +11,7 @@
 
 import {StyleSheet, ViewStyle, StyleProp, KeyboardAvoidingView, Platform} from 'react-native';
 import {Portal, Modal} from 'react-native-paper';
-import {DTColors} from '../theme/colors';
+import {useDTTheme} from '../theme/DTThemeProvider';
 import {type DTVariant} from '../utils/variantColors';
 import {DTCard} from './DTCard';
 
@@ -75,6 +75,8 @@ export function DTModal({
   contentStyle,
   style,
 }: DTModalProps) {
+  const theme = useDTTheme();
+
   return (
     <Portal>
       <Modal
@@ -85,7 +87,7 @@ export function DTModal({
         style={styles.modal}
         theme={{
           colors: {
-            backdrop: DTColors.overlay,
+            backdrop: theme.colors.backdrop,
           },
         }}>
         <KeyboardAvoidingView