Make whales spawn randomly across entire screen

- Changed whale spawn from center area to full screen
- X position: 100-700 (was 350-450)
- Y position: 150-500 (was 250-350)
- Each whale now appears in unpredictable location
- Keeps margins to avoid edge spawning
- Increases gameplay variety and challenge

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/scenes/HuntingScene.js

@@ -244,9 +244,9 @@ export default class HuntingScene extends Phaser.Scene {
             return;
         }
 
-        // Spawn in center area with some variation
-        const x = 350 + Math.random() * 100; // 350-450 (center area)
-        const y = 250 + Math.random() * 100; // 250-350 (center area)
+        // Spawn randomly all over the screen
+        const x = 100 + Math.random() * 600; // 100-700 (across screen with margins)
+        const y = 150 + Math.random() * 350; // 150-500 (across screen with margins)
         const direction = Math.random() > 0.5 ? 1 : -1;
 
         // Create whale body