Add request logging mode, dark mode, Account hub, profile, vehicle CRUD, cards view

- Client: logRequests option + redacted request/response logging (setLogRequests to
  toggle at runtime); enabled via app extra.debugHttp for on-device 401 debugging
- Dark mode (persisted) via ThemeProvider + React Navigation theme
- New "Account" tab: Profile (view), Vehicles (full CRUD), Payment methods (view-only),
  About, dark-mode + request-logging toggles, sign out

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/theme/ThemeContext.tsx

@@ -0,0 +1,102 @@
+import React, {
+  createContext,
+  useContext,
+  useEffect,
+  useMemo,
+  useState,
+} from 'react';
+import AsyncStorage from '@react-native-async-storage/async-storage';
+import {
+  DarkTheme as NavDark,
+  DefaultTheme as NavLight,
+  type Theme as NavTheme,
+} from '@react-navigation/native';
+
+export type ThemeMode = 'light' | 'dark';
+
+export interface Colors {
+  bg: string;
+  card: string;
+  text: string;
+  subtext: string;
+  border: string;
+  primary: string;
+  danger: string;
+}
+
+const light: Colors = {
+  bg: '#ffffff',
+  card: '#f4f4f4',
+  text: '#111111',
+  subtext: '#666666',
+  border: '#e0e0e0',
+  primary: '#1e6f5c',
+  danger: '#c0392b',
+};
+
+const dark: Colors = {
+  bg: '#0e1513',
+  card: '#1b2422',
+  text: '#f2f2f2',
+  subtext: '#9aa5a1',
+  border: '#2c3a36',
+  primary: '#3fbf9c',
+  danger: '#ef6a5c',
+};
+
+interface ThemeState {
+  mode: ThemeMode;
+  colors: Colors;
+  navTheme: NavTheme;
+  setMode: (m: ThemeMode) => void;
+  toggle: () => void;
+}
+
+const ThemeContext = createContext<ThemeState | null>(null);
+const STORAGE_KEY = 'ps_theme_mode';
+
+export function ThemeProvider({ children }: { children: React.ReactNode }) {
+  const [mode, setModeState] = useState<ThemeMode>('light');
+
+  useEffect(() => {
+    AsyncStorage.getItem(STORAGE_KEY).then((v) => {
+      if (v === 'light' || v === 'dark') setModeState(v);
+    });
+  }, []);
+
+  const setMode = (m: ThemeMode) => {
+    setModeState(m);
+    void AsyncStorage.setItem(STORAGE_KEY, m);
+  };
+
+  const value = useMemo<ThemeState>(() => {
+    const colors = mode === 'dark' ? dark : light;
+    const base = mode === 'dark' ? NavDark : NavLight;
+    const navTheme: NavTheme = {
+      ...base,
+      colors: {
+        ...base.colors,
+        background: colors.bg,
+        card: colors.bg,
+        text: colors.text,
+        border: colors.border,
+        primary: colors.primary,
+      },
+    };
+    return {
+      mode,
+      colors,
+      navTheme,
+      setMode,
+      toggle: () => setMode(mode === 'dark' ? 'light' : 'dark'),
+    };
+  }, [mode]);
+
+  return <ThemeContext.Provider value={value}>{children}</ThemeContext.Provider>;
+}
+
+export function useTheme(): ThemeState {
+  const ctx = useContext(ThemeContext);
+  if (!ctx) throw new Error('useTheme must be used within ThemeProvider');
+  return ctx;
+}