fix: replace broken search plugin with local search implementation

[PratikshaJ-16]

Fix: Search bar not working in development

Problem:

The search bar in the navbar was not functioning correctly:

• Clicking showed no results
• Displayed "Loading..." or inactive state
• Search plugin (docusaurus-lunr-search) was not working properly

##Solution:

• Replaced the existing search plugin with a maintained alternative:
  @easyops-cn/docusaurus-search-local
• Updated docusaurus.config.js to integrate the new plugin
• Installed and configured the plugin for proper indexing

Testing:

• Verified search functionality locally using:
  • npm start (dev mode)
  • npm run build + npm run serve (production mode)
• Search results now appear correctly and are interactive

Impact:

• Fixes broken search UI in navbar
• Improves user experience and navigation
• Ensures reliable local search functionality without external services