fix: Update Algolia search credentials

[sentry]

This PR addresses issue BLOG-5T where Algolia search was failing with a "RetryError: Unreachable hosts" due to incorrect appId and apiKey being hardcoded in the DocSearch component.

Changes Made:

• Replaced the hardcoded appId and apiKey in src/components/docsearch-react.tsx with references to environment variables (import.meta.env.PUBLIC_ALGOLIA_APP_ID and import.meta.env.PUBLIC_ALGOLIA_API_KEY).
• Declared PUBLIC_ALGOLIA_APP_ID and PUBLIC_ALGOLIA_API_KEY as required string environment variables in src/env.d.ts to ensure type safety and proper configuration.

Impact:
Algolia search will now function correctly once the PUBLIC_ALGOLIA_APP_ID and PUBLIC_ALGOLIA_API_KEY environment variables are set with the correct values in the deployment environment.

Fixes BLOG-5T

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