Function getClosestRegionFromIP

getClosestRegionFromIP(request: Request): D1Region
Determines the closest D1 region based on an IP address. Uses IP geolocation to estimate the user's location and find the nearest D1 region.

This function uses Cloudflare's CF object which provides geolocation data in Cloudflare Workers environment. Falls back to 'wnam' if geolocation fails.
Parameters
- request: Request
  The incoming Request object (contains CF geolocation data in Cloudflare Workers)
Returns D1Region
The closest D1Region based on IP geolocation
Example
```
// In a Cloudflare Worker
export default {
  async fetch(request: Request, env: Env) {
    const userRegion = getClosestRegionFromIP(request);

    initialize({
      kv: env.KV,
      strategy: 'location',
      targetRegion: userRegion, // Automatically optimized for user location
      shardLocations: { ... },
      shards: { ... }
    });
  }
};
```
- Defined in src/router.ts:390