fix: resolve Google TTS 200-character limit video render crash

[angelina-2206]

Description

This PR resolves the 200-character limit crash in the Google Text-to-Speech API (google-tts-api@0.0.6) during video generation. Long narration texts generated by the AI are now split into word-aligned chunks under 200 characters, fetched separately, and stitched together using Buffer.concat to produce a single audio asset.

Additionally, this PR:

1. Fixes a request body stream consumption crash in the /api/video/generate route by replacing the double req.json() call with the validated data object.
2. Resolves syntax, duplicate declaration, and merge errors inherited from upstream/main in auth pages, doubts, and replies API routes to restore build compilation.

Related Issue

Closes #272

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Documentation update (README, guides, comments)
• Style / UI change (no logic change)
• Code refactor (no behavior change)
• Test addition or update
• Breaking change (fix or feature that would cause existing functionality to change)

How Has This Been Tested?

• Tested locally with npm run dev (verified with npm run build and npm run test)

Checklist

• I have tested my changes locally (npm run dev)
• My code follows the existing code style (TypeScript, Tailwind, no any types)
• I have not introduced unrelated changes (each PR should address one issue)
• I have added comments where necessary
• My branch is up to date with main
• I have linked the related issue above

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[knoxiboy]

Automated review: Thank you for starring the repository! The PR is approved.
Note: This PR currently has merge conflicts with the main branch. Please resolve the merge conflicts so we can complete the merge!

[Copilot]

Pull request overview

This PR addresses the video generation crash caused by Google TTS text-length limits and also cleans up several API/auth compilation issues.

Changes:

• Replaces direct google-tts-api usage with chunked Google TTS URL generation and audio buffer concatenation.
• Uses validated request data in video generation instead of reading the request body twice.
• Removes broken duplicate auth page code and fixes small API route typing/destructuring issues.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
app/api/video/generate/route.ts	Adds TTS chunking/audio stitching and fixes request body reuse.
app/api/replies/vote/route.ts	Removes duplicate body parsing after validation.
app/api/replies/route.ts	Uses validated numeric doubtId directly.
app/api/replies/action/[id]/route.ts	Removes unused destructured fields from validated data.
app/api/doubts/route.ts	Adds explicit array typing for reassigned doubt results.
app/(auth)/sign-up/[[...sign-up]]/page.tsx	Removes duplicated malformed component code and restores themed sign-up page.
app/(auth)/sign-in/[[...sign-in]]/page.tsx	Removes duplicated malformed component code and restores themed sign-in page.

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[knoxiboy]

Hi there! 👋 Thanks for your contribution to DoubtDesk.

It looks like there are currently some merge conflicts between your branch and the main branch. Could you please pull the latest changes from main, resolve the conflicts, and push the updates to this branch?

Once the conflicts are resolved and the PR is clean, we'll be able to merge it!