Task 1b: Rebuild boot sequence and ECG animation

- Refactored BootSequence to config-driven architecture with type-safe line components
- Added cursor position capture and smooth cursor-to-dot morph transition
- Rebuilt ECGAnimation with mask-based text reveal technique
- Implemented connector lines between letters with per-character profiles
- ECG trace now starts from cursor position (no teleport)
- Added prefers-reduced-motion support for both phases
- Updated App.tsx to pass cursor position between components

Quality checks: typecheck ✓, lint ✓, build ✓

src/App.tsx

@@ -1,4 +1,4 @@
-import { useState } from 'react'
+import { useState, useCallback } from 'react'
 import type { Phase } from './types'
 import { BootSequence } from './components/BootSequence'
 import { ECGAnimation } from './components/ECGAnimation'
@@ -8,20 +8,43 @@ import { AccessibilityProvider } from './contexts/AccessibilityContext'
 
 function App() {
   const [phase, setPhase] = useState<Phase>('boot')
+  const [cursorPosition, setCursorPosition] = useState<{ x: number; y: number } | null>(null)
+
+  const handleBootComplete = useCallback(() => {
+    setPhase('ecg')
+  }, [])
+
+  const handleCursorPositionReady = useCallback((position: { x: number; y: number }) => {
+    setCursorPosition(position)
+  }, [])
+
+  const handleECGComplete = useCallback(() => {
+    setPhase('login')
+  }, [])
+
+  const handleLoginComplete = useCallback(() => {
+    setPhase('pmr')
+  }, [])
 
   return (
     <AccessibilityProvider>
       <div className="min-h-screen bg-black">
         {phase === 'boot' && (
-          <BootSequence onComplete={() => setPhase('ecg')} />
+          <BootSequence 
+            onComplete={handleBootComplete} 
+            onCursorPositionReady={handleCursorPositionReady}
+          />
         )}
         
         {phase === 'ecg' && (
-          <ECGAnimation onComplete={() => setPhase('login')} />
+          <ECGAnimation 
+            onComplete={handleECGComplete} 
+            startPosition={cursorPosition}
+          />
         )}
         
         {phase === 'login' && (
-          <LoginScreen onComplete={() => setPhase('pmr')} />
+          <LoginScreen onComplete={handleLoginComplete} />
         )}
         
         {phase === 'pmr' && <PMRInterface />}