FEATURE REQUEST: Upgrade deprecated dependencies and Gradle versions

### Is your feature request related to a problem?

- [x] Yes, it is related to a problem

### Describe the feature you'd like

## 🌟 Feature Description
Upgrade deprecated dependencies and Gradle versions to ensure compatibility with the latest Flutter SDK and Android tooling.
This includes updating google_sign_in, speech_to_text, Android Gradle Plugin, and Kotlin to supported versions, along with necessary code adjustments for google_sign_in v7.

## 🔍 Problem Statement
The project currently relies on outdated dependencies:

- google_sign_in (^6.x.x) → deprecated, conflicts with current Flutter SDK.
- speech_to_text (older version) → missing bug fixes and stability updates.
- Android Gradle Plugin (8.2.1) and Kotlin (1.8.22) → both deprecated and flagged for removal in upcoming Flutter releases.

These cause build warnings, version conflicts, and reduced compatibility with modern development tools.

## 🎯 Expected Outcome

- All affected dependencies upgraded to latest stable versions:
- google_sign_in: ^7.x.x
- speech_to_text: ^6.x.x
- AGP → 8.5.2
- Kotlin → 1.9.25
- Code updated for google_sign_in v7 breaking changes.
- Project builds successfully on the latest Flutter SDK without deprecation warnings.
- Verified smooth sign-in and speech recognition functionality after upgrades.

### Record

- [x] I agree to follow this project's Code of Conduct
- [x] I want to work on implementing this feature