Add Playwright E2E testing with recorded workflows

- Add @playwright/test as dev dependency
- Create playwright.config.ts with Chrome-only testing config
- Add npm scripts: test:record, test:e2e, test:replay
- Create 13 test recordings covering:
  - 2-player and 3-player games
  - 8-ball, 9-ball, and 10-ball game types
  - Various race-to values (1, 3, 5, 7, 9) and "endlos" mode
  - Both wechselbreak (alternating) and winnerbreak rules
- Fix Infinity handling in gameService.ts and NewGameScreen.tsx
  - Parse "endlos" and "Infinity" strings as Infinity number
  - Properly serialize Infinity as string in form data
- Increase GameDetail score font size from 20vh to 40vh
- Update README.md with testing documentation:
  - Quick start guide for recording and running tests
  - Move E2E testing from "Future Improvements" (now implemented)
- Add comprehensive tests/recordings/README.md documentation

Purpose: Establishes browser automation testing infrastructure with
real workflow recordings, enabling regression testing and interaction
documentation for all game configuration combinations.

src/components/GameDetail.module.css

@@ -120,7 +120,7 @@
     color: #222;
 }
 .score {
-    font-size: 20vh;
+    font-size: 40vh;
     font-weight: 900;
     margin: 20px 0 30px 0;
     line-height: 1;

src/components/screens/NewGameScreen.tsx

@@ -63,10 +63,12 @@ export default function NewGameScreen({
     onCreateGame(finalData as any);
   };
 
-  const handleRaceToNext = (raceTo: string) => {
-    const finalData = { ...data, raceTo };
+  const handleRaceToNext = (raceTo: string | number) => {
+    // Convert to string, handling Infinity case explicitly
+    const raceToStr = raceTo === Infinity ? 'Infinity' : String(raceTo);
+    const finalData = { ...data, raceTo: raceToStr };
     // After race to, go to break rule selection
-    onDataChange({ raceTo });
+    onDataChange({ raceTo: raceToStr });
     onStepChange('breakRule');
   };