Upgrade TailwindCSS to 4.1.8

[Copilot]

Upgrades TailwindCSS from 3.4.17 to 4.1.8 in webapp/_webapp. TailwindCSS v4 introduces a new architecture requiring plugin and import syntax changes.

Changes

• Dependencies: Added @tailwindcss/postcss@4.1.8, updated tailwindcss to 4.1.8
• PostCSS config: Use @tailwindcss/postcss plugin instead of tailwindcss
• CSS imports: Replace three @tailwind directives with single @import "tailwindcss"
• Config format: Convert tailwind.config.js from CommonJS to ES modules

Before/After

/* v3 syntax */
@tailwind base;
@tailwind components;
@tailwind utilities;

/* v4 syntax */
@import "tailwindcss";

// v3 config
const { heroui } = require("@heroui/react");
module.exports = { /* config */ };

// v4 config  
import { heroui } from "@heroui/react";
export default { /* config */ };

No changes to theme configuration or plugin setup required.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• buf.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/_temp/ghcca-node/node/bin/npm install (dns block)
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/_temp/ghcca-node/node/bin/npm install --prefer-offline (dns block)
• tailwindcss.com
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.