Create user timezone activity normalizer

## Description
Normalize activity metrics by user timezone for accurate global insights.

## Requirements
- Timezone detection from coordinates
- Activity normalization by local time
- Global peak hour adjusted chart
- Timezone distribution map
- UTC vs local time toggle

## Files to Touch
- analytics/app/timezone-analysis/page.tsx
- analytics/lib/timezone-normalizer.ts

**Complexity: 200 points**