fix(know-your-world): use shared MAX_ZOOM constant for mobile magnifier

Replace local MAX_ZOOM = 50 with shared MAX_ZOOM = 1000 from constants.
This fixes mobile magnifier auto-zoom being incorrectly capped at 50x
when panning within the magnifier, while map dragging was uncapped.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/arcade-games/know-your-world/features/magnifier/useMagnifierTouchHandlers.ts

@@ -19,6 +19,7 @@ import { findOptimalZoom } from '../../utils/adaptiveZoomSearch'
 import { getMagnifierDimensions } from '../../utils/magnifierDimensions'
 import { useMapGameContext } from '../game'
 import { getRenderedViewport } from '../labels'
+import { MAX_ZOOM } from '../shared/constants'
 import { useMagnifierContext } from './MagnifierContext'
 import { calculateTouchMultiplier, clampToSvgBounds, parseViewBoxDimensions } from './panningMath'
 
@@ -26,7 +27,6 @@ import { calculateTouchMultiplier, clampToSvgBounds, parseViewBoxDimensions } fr
 // Constants
 // ============================================================================
 
-const MAX_ZOOM = 50
 const SAFE_ZONE_MARGINS = {
   top: 60,
   right: 8,