🧹 Remove explicit 'any' from window object and strongly type custom properties

[kuasar-mknd]

🎯 What: Removed the explicit any type assertion on the window object (const win = window as any;) across multiple .astro files and correctly extended the Window interface in src/env.d.ts with strict types for all attached custom properties used for singleton listeners and logic.
💡 Why: Explicit any assertions bypass TypeScript's type checking, creating a risk for typos and unsafe property access. By adding these global event handlers and observer properties to the global Window interface, we achieve full type safety and clearer developer intent. It conforms better to the @typescript-eslint/no-explicit-any linting rule.
✅ Verification: Ran pnpm run check (formatter, linter, type checker), which successfully passed. Also ran pnpm run build and pnpm run test:e2e, verifying that these refactors did not introduce any regressions and end-to-end functionality (like lightbox, theme toggle, auto-resizing textareas) remains completely intact.
✨ Result: A safer, more robustly typed codebase with properly defined global singleton listeners and better DX due to autocompletion for window.__* properties.

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PR created automatically by Jules for task 15537727034846077092 started by @kuasar-mknd

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