Redesign session UX: progress ring, round markers, red theme

- Animated ring sweeps the timer edge in proportion to the current step
  (react-native-svg), matching the meditation-timer idiom
- Per-block round markers: circle = squeeze, square = push, X = quick
  flicks; small interleaved dots distinguish rest rounds from work rounds
- Stamena-style red theme throughout (bg, accent, splash, adaptive icon)
- Home screen legend teaching the shape vocabulary

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

package.json

@@ -18,6 +18,7 @@
     "react-native": "0.86.2",
     "react-native-safe-area-context": "~5.7.0",
     "react-native-screens": "~4.26.0",
+    "react-native-svg": "15.15.4",
     "react-native-web": "^0.21.2"
   },
   "devDependencies": {