⚡ Bolt: optimize PageTransition event listeners to prevent memory leaks

[kuasar-mknd]

💡 What: Refactored PageTransition.astro to use the Singleton Listener pattern for astro:before-preparation, astro:after-preparation, and document click events.
🎯 Why: Astro View Transitions can re-evaluate component scripts during navigation, causing anonymous event listeners to stack and execute redundantly, leading to memory leaks and performance degradation on the client side.
📊 Impact: Eliminates unbounded growth of global event listeners, preventing redundant main-thread executions and memory leaks on repeated page navigations.
🔬 Measurement: Verified locally using Playwright; the number of active event listeners on document and window no longer increases linearly with each page transition, maintaining a stable baseline memory footprint.

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PR created automatically by Jules for task 3919580246294493363 started by @kuasar-mknd

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