chore: remove v1 features and old scaffolding

Remove onboarding flow (6 screens), timer engine, audio engine,
old components (themed-text/view, parallax-scroll, hello-wave),
old constants (theme, shadows, timer), and utility files that
were replaced by the v2 architecture.

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

src/shared/constants/shadows.ts

@@ -1,44 +0,0 @@
-import type { TextStyle, ViewStyle } from 'react-native'
-
-export const SHADOW = {
-  BRAND_GLOW: {
-    shadowColor: '#F97316',
-    shadowOffset: { width: 0, height: 4 },
-    shadowOpacity: 0.5,
-    shadowRadius: 20,
-    elevation: 12,
-  } as ViewStyle,
-
-  WHITE_GLOW: {
-    shadowColor: '#FFFFFF',
-    shadowOffset: { width: 0, height: 0 },
-    shadowOpacity: 0.8,
-    shadowRadius: 6,
-  } as ViewStyle,
-} as const
-
-export const TEXT_SHADOW = {
-  BRAND: {
-    textShadowColor: 'rgba(249, 115, 22, 0.5)',
-    textShadowOffset: { width: 0, height: 0 },
-    textShadowRadius: 30,
-  } as TextStyle,
-
-  WHITE_SOFT: {
-    textShadowColor: 'rgba(255, 255, 255, 0.25)',
-    textShadowOffset: { width: 0, height: 0 },
-    textShadowRadius: 30,
-  } as TextStyle,
-
-  WHITE_MEDIUM: {
-    textShadowColor: 'rgba(255, 255, 255, 0.3)',
-    textShadowOffset: { width: 0, height: 0 },
-    textShadowRadius: 20,
-  } as TextStyle,
-
-  DANGER: {
-    textShadowColor: 'rgba(239, 68, 68, 0.6)',
-    textShadowOffset: { width: 0, height: 0 },
-    textShadowRadius: 40,
-  } as TextStyle,
-} as const

src/shared/constants/timer.ts

@@ -1,10 +0,0 @@
-export const TIMER_DEFAULTS = {
-  WORK_DURATION: 20,
-  REST_DURATION: 10,
-  ROUNDS: 8,
-  GET_READY_DURATION: 10,
-  CYCLES: 1,
-  CYCLE_PAUSE_DURATION: 60,
-} as const
-
-export const TICK_INTERVAL_MS = 100