feat: remove ECG phase entirely

- Deleted src/components/ECGAnimation.tsx (686 lines)
- Removed 'ecg' from Phase type
- Removed ECG import, rendering, and cursor position handoff from App.tsx
- Cleaned up BootSequence: removed onCursorPositionReady prop,
  captureCursorPosition callback, cursorRef, and ECG-specific naming
- Renamed ecgStartDelay → completionDelay, ecg-seed-dot → boot-seed-dot
- Skip button now goes directly to dashboard ('pmr' phase)
- Boot flow simplified: boot → login → pmr (no ECG intermediary)
- Bundle size reduced ~8KB

src/index.css

@@ -77,7 +77,7 @@
 }
 
 :root {
-  /* Original design system tokens (for boot/ECG phases) */
+  /* Original design system tokens (for boot phase) */
   --bg: #FFFFFF;
   --text: #334155;
   --heading: #0F172A;