Update add-on to app terminology per hacs/addons#37

[Copilot]

Reflects terminology change from hacs/addons#37 per HA architecture discussion #1287: user-facing "Add-on" → "App" for the Get HACS tool.

Changes

• faq/addons.md: "Get HACS add-on" → "Get HACS app"
• download/prerequisites.md: "add-on to download HACS" → "app to download HACS"
• download/download.md: Updated installation instructions to reference "app" for the Get HACS tool

Preserved (intentionally)

• "add-on repository" references — the repository is still technically an add-on repository
• HA UI references like "Missing add-on repository" dialog
• External links to HA add-on glossary

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:

• cdn.jsdelivr.net
  • Triggering command: /home/REDACTED/.local/bin/mkdocs mkdocs build --strict (dns block)
• fonts.google.com
  • Triggering command: /home/REDACTED/.local/bin/mkdocs mkdocs build --strict (dns block)
• unpkg.com
  • Triggering command: /home/REDACTED/.local/bin/mkdocs mkdocs build --strict (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)

Original prompt

Make sure the documentation reflects the changes in hacs/addons#37

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