Add Tailwind integration, custom asset output, image loader fixes, and theme/theme variable updates

[alaster-t34]

Motivation

• Integrate Tailwind and simplify PostCSS to enable utility-driven styling and consistent build output.
• Ensure static assets are emitted into a predictable assets/ folder with stable hashed filenames for GitHub Pages compatibility.
• Improve local image dynamic import resolution and typing to avoid missing image lookups at runtime.
• Refresh theme variables and CSS to use a hue-driven design system and updated layout visuals.

Description

• Enable @astrojs/tailwind in astro.config.mjs, add build.assets setting and customize Vite/Rollup assetFileNames, chunkFileNames, and entryFileNames to output into assets/ with safe names using node:path.
• Change HMR/server watch options and include a .nojekyll in public/ to prevent Jekyll processing on GitHub Pages.
• Simplify postcss.config.mjs to only include postcss-import and remove direct Tailwind/PostCSS nesting plugin usage.
• Replace path imports with node:path and update ImageWrapper.astro to type img as ImageMetadata, expand import.meta.glob to search assets and content directories, normalize paths, and improve error logging.
• Adjust layout and component imports in MainGridLayout.astro, wire up ImageWrapper and TOC, and tidy prop destructuring and mainPanelTop calculation.
• Overhaul styles: update src/styles/main.css to use a background image and simplified navbar/card backdrop styles, tweak markdown link styling in src/styles/markdown.css, and substantially refactor theme tokens in src/styles/variables.styl to use var(--hue) and new Oklch-based tokens; also change --radius-large.
• Minor typing/formatting fixes in src/utils/content-utils.ts and bump default theme hue in src/config.ts from 205 to 250.

Testing

• Ran a production build (npm run build) to validate the Astro/Vite build pipeline and asset emission, which completed successfully.
• Confirmed there are no project unit tests included in the repo to run with npm test (none present).

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Codex Task