Some small UI wording changes

[ajp-io]

What this PR does / why we need it:

Changes the wording in a few ways:

• Slightly different subheading on the setup page about setting up hosts
• Lowercase extensions except when they're used as a title. Under the progress bar it'll say, "Installing storage," but the storage section on the installation page will say "Storage."
• Don't show error message under the progress bar since it's already at the bottom of the page. Say "Installation failed" instead.
• Add ellipsis … to the text under the progress bar
• Makes checkmark icon the right color

2025-06-17_20-41-40.mp4

[github-actions]

This PR has been released (on staging) and is available for download with a embedded-cluster-smoke-test-staging-app license ID.

Online Installer:

curl "https://staging.replicated.app/embedded/embedded-cluster-smoke-test-staging-app/ci/appver-dev-670cedb" -H "Authorization: $EC_SMOKE_TEST_LICENSE_ID" -o embedded-cluster-smoke-test-staging-app-ci.tgz

Airgap Installer (may take a few minutes before the airgap bundle is built):

curl "https://staging.replicated.app/embedded/embedded-cluster-smoke-test-staging-app/ci-airgap/appver-dev-670cedb?airgap=true" -H "Authorization: $EC_SMOKE_TEST_LICENSE_ID" -o embedded-cluster-smoke-test-staging-app-ci.tgz

Happy debugging!