[Docs] Fix 404 asset base path for previews

[CodexRaunak]

Root cause: Relative URL = true, this makes the site assets, paths, relative to the current page location, I originally added this to make the assets/paths resolve correctly when deployed under a sub path like pr-previews.

But that's was a symptom level fix, accumulating more technical debt than solving the problem. It resolves correctly for pages except 404 as GitHub Pages serves one 404.html from many URL depths, causing the browser to resolve those relative asset URLs against arbitrary missing paths.

Proposed Fix: For a stronger architecture, relative URLs are set to false, so that Hugo generates URLs as per the site base URL rather than rewriting every URL relative to the current page, as it's fragile as it's correctness depends on the depth of the current URL depth not being served from the site base.

Changes made:
Used relURL for shared assets in templates. This ensures asset paths are generated relative to the configured baseURL.
Used Hugo ref helper for Markdown links (inter page links) eg: removing the hardcoded paths from /concepts/architecture/index.md to {{< ref "concepts/architecture/index.md" >}}. It make the paths resolve correctly when site is served under different baseURLs.
Updated image references to use:
images/instead of hardcoded root-based paths.
Restructured the docs
Previously, many page-specific assets were stored in section-level images/ directories, creating an implicit relationship between content and assets. This made pages harder to move and maintain because asset ownership was not represented in the filesystem.
The restructure converts content to consistent page bundles and colocates assets with the pages that own them.
Ownership Model:
Pages without local resources should remain standalone Markdown files.
Pages with local resources should use page bundles:
page/
├── index.md
└── images/
└── image-name.png
Section-level shared assets belong in the section’s images/ folder.

[gemini-code-assist]

Code Review

This pull request adds a script block to layouts/partials/head.html for 404 pages to dynamically set the <base> tag's href attribute when in a PR preview environment. The reviewer suggested updating the JavaScript variable declarations from var to const to align with modern standards and improve block-scoping.

[github-actions]

🚀 Preview deployment: https://layer5io.github.io/docs/pr-preview/pr-1066/

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[Bhumikagarggg]

Hey @CodexRaunak!
You can close this PR. I’ve made the correct changes and verified them locally for this issue in PR #1077.