Add CV page and refresh homepage; update name/title and portfolio styles

[gokul-github]

Motivation

• Consolidate personal branding by using the full name and updated professional title across the site.
• Surface a full CV and refreshed homepage to better present experience, skills, and contact details for product/architect roles.
• Improve styling for the portfolio/hero area to make the profile and quick facts clearer on different screen sizes.

Description

• Updated _config.yml to use the full name Gokulnath Avanashilingam and preserve site settings.
• Modified _includes/head.html to update the page title and author metadata to the new full name and senior title.
• Extended css/style.css with new portfolio-specific styles (hero section, profile links, quick-facts, skill and experience presentation).
• Reworked index.html to add a hero/profile section, contact info, highlights, core skills, recent focus, and an experience preview with a link to the CV.
• Added a new cv/index.html page containing a full CV with profile, skills, work history, education, courses, languages, and interests.

Testing

• Ran jekyll build locally to validate that the site generates without errors and the new pages are included successfully (build completed successfully).
• No additional automated unit tests were added as this change is content and presentation focused.

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Codex Task