fix(ai-voice): resolve speech recognition typescript and closure errors

[Mohammad-Hassan027]

Description

This PR resolves the TypeScript compilation failures affecting the Web Speech API implementations across the project, specifically addressing the issues in the AI Voice page.

Changes introduced:

• Created types/speech-recognition.d.ts as a single, authoritative global ambient declaration for the Web Speech API.
• Removed conflicting, module-scoped SpeechRecognition interfaces from app/(dashboard)/ai-voice/page.tsx, app/(dashboard)/ai-tutor/page.tsx, and app/(dashboard)/ai-tutor/old-page.tsx which were causing TS2717 clashes.
• Fixed a stale closure bug (TS2367) in the onend event handler of ai-voice/page.tsx by implementing a voiceStateRef to properly track the live state inside async callbacks.

Related Issue: Closes #76

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update (non-breaking change to add/edit documentation)

How Has This Been Tested?

• TypeScript Compiler: Ran npx tsc --noEmit locally. Verified that all previous SpeechRecognition name/property errors (TS2304, TS2717, TS2339, TS2551) in ai-voice and ai-tutor are fully resolved.
• State Logic: Verified that the AI Voice page's event listeners correctly reference voiceStateRef.current instead of a stale captured voiceState, allowing the UI to reset properly after speech ends.

Visual Proof (Screenshots/GIFs/Videos):
N/A — This is primarily a type-safety and internal state management fix. No visible UI design changes were made.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings/lint errors
• I have checked that my branch is up-to-date with main
• All tests pass locally with my changes

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