chore(tangle-dapp): Update modals (header, footer, body)

[devpavan04]

Summary of changes

• Modal footer with dual buttons are stacked horizontally rather than vertically.
• Modal background uses monochrome/180 color.

Proposed area of change

Put an x in the boxes that apply.

• [ ] apps/bridge-dapp
• [ ] apps/hubble-stats
• [ ] apps/stats-dapp
• [x] apps/tangle-dapp
• [ ] apps/testnet-leaderboard
• [ ] apps/faucet
• [ ] apps/zk-explorer
• [x] libs/webb-ui-components

Reference issue to close (if applicable)

• Closes #2476

Screenshots

[netlify[bot]]

✅ Deploy Preview for tangle-dapp ready!

Name	Link
🔨 Latest commit	49dd67f7e39ecd404dad1ef42eb90e0d6d1a4a42
🔍 Latest deploy log	https://app.netlify.com/sites/tangle-dapp/deploys/66b33d5212a73100088fc489
😎 Deploy Preview	https://deploy-preview-2506--tangle-dapp.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.