Add PostCSS configuration and skills lock file

- Created a new PostCSS configuration file to integrate Tailwind CSS.
- Added a skills lock file containing various Expo skills with their respective source and computed hashes.

.agents/skills/upgrading-expo/references/react-compiler.md

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+# React Compiler
+
+React Compiler is stable in Expo SDK 54 and later. It automatically memoizes components and hooks, eliminating the need for manual `useMemo`, `useCallback`, and `React.memo`.
+
+## Enabling React Compiler
+
+Add to `app.json`:
+
+```json
+{
+  "expo": {
+    "experiments": {
+      "reactCompiler": true
+    }
+  }
+}
+```
+
+## What React Compiler Does
+
+- Automatically memoizes components and values
+- Eliminates unnecessary re-renders
+- Removes the need for manual `useMemo` and `useCallback`
+- Works with existing code without modifications
+
+## Cleanup After Enabling
+
+Once React Compiler is enabled, you can remove manual memoization:
+
+```tsx
+// Before (manual memoization)
+const memoizedValue = useMemo(() => computeExpensive(a, b), [a, b]);
+const memoizedCallback = useCallback(() => doSomething(a), [a]);
+const MemoizedComponent = React.memo(MyComponent);
+
+// After (React Compiler handles it)
+const value = computeExpensive(a, b);
+const callback = () => doSomething(a);
+// Just use MyComponent directly
+```
+
+## Requirements
+
+- Expo SDK 54 or later
+- New Architecture enabled (default in SDK 54+)
+
+## Verifying It's Working
+
+React Compiler runs at build time. Check the Metro bundler output for compilation messages. You can also use React DevTools to verify components are being optimized.
+
+## Troubleshooting
+
+If you encounter issues:
+
+1. Ensure New Architecture is enabled
+2. Clear Metro cache: `npx expo start --clear`
+3. Check for incompatible patterns in your code (rare)
+
+React Compiler is designed to work with idiomatic React code. If it can't safely optimize a component, it skips that component without breaking your app.