🧹 [code health improvement] Remove explicit 'any' from window object and augment Window interface

[kuasar-mknd]

🎯 What: Removed the explicit 'any' type cast for the window object in various .astro files and augmented the Window interface in src/env.d.ts to type custom singleton properties properly.
💡 Why: Overusing any bypasses TypeScript checks. By strictly typing properties on Window, we enforce type safety for DOM event listeners and state flags, removing ESLint ignore directives.
✅ Verification: Ran pnpm check (format, lint, typecheck) to ensure code compiles and follows standards. Verified locally with Playwright E2E tests, which all passed, confirming that the changes introduce no functional side effects.
✨ Result: Better type safety, cleaner source files without ESLint comments, and improved code autocompletion.

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PR created automatically by Jules for task 13684531248846941080 started by @kuasar-mknd

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