refactor(ui): resolve duplicate ID conflicts for global controls

[Shashank-8p]

📝 Description

Resolves a critical DOM architecture issue where duplicate IDs (themeToggle, soundToggle) were causing cross-component conflicts and breaking the UI controls.

Architectural Changes Implemented:

• HTML Cleanup: Stripped duplicate id attributes from the navigation, sidebar, and hero control buttons, retaining only their functional classes.
• JS Refactor: Replaced fragile getElementById targeting with querySelectorAll('.theme-toggle') and .forEach() loops.
• Synchronization: Removed the legacy "click mirroring" hack. The new class-based event listeners now natively synchronize state and icons across all instances of a button on the page simultaneously.

🔗 Linked Issue

Closes #921

---

📋 Contribution Checklist

• My code strictly adheres to the project guidelines.
• I have verified in the DOM inspector that the duplicate IDs no longer exist.
• GSSoC 2026: I have been formally assigned to this issue and noted it above.

[vercel]

@Shashank-8p is attempting to deploy a commit to the Anuj's projects Team on Vercel.

A member of the Team first needs to authorize it.