[BUG 976] Make useLocalInstall() more complete

[alanhargreaves]

What does this PR do?

• Makes useLocalInstall() check a few more domain names
• Tidies up useLocalInstall()
• Removes extra instances of isLocalInstall (passing the one copy around) and reduces the calls to useLocalInstall to teh single call in App
• Adds a .env variable called localServer, which defaults to false. If this is set to true it will override all other checks in `useLocalInstall()

Type of change

• Bug fix
• New feature
• Performance improvement
• Refactor / code cleanup
• Documentation
• Translation
• Map layer plugin

How to test

TODO

Checklist

• App loads without console errors
• Tested in Dark, Light, and Retro themes
• Responsive at different screen sizes (desktop + mobile)
• If touching server.js: caches have TTLs and size caps (we serve 2,000+ concurrent users)
• If adding an API route: includes caching and error handling
• If adding a panel: wired into Modern, Classic, and Dockable layouts
• No hardcoded colors — uses CSS variables (var(--accent-cyan), etc.)
• No .bak, .old, console.log debug lines, or test scripts included

Screenshots (if visual change)

[accius]

Good direction overall. Adding the .home / .lan / .internal host patterns expands coverage cleanly, and hoisting the useLocalInstall() call up to App and passing the boolean down via props eliminates the duplicate hook calls in SettingsPanel/WorldMap. The serverLocal env-driven override is a useful escape hatch for unusual deployments (Tailscale, reverse-proxied LAN hosts on public-looking domains, etc.).

Two things before this is ready to come out of draft:

1. The "How to test" section in the PR description is still TODO — please fill that in so reviewers (and future you) can validate the expanded host pattern matrix and the serverLocal override path.
2. The frontend reads serverCfg.serverLocal in useAppConfig.js, but I don't see the corresponding server-side change that surfaces that field through /api/config (or wherever getServerConfig() resolves). If that lives in another commit on the branch, great — otherwise it'll need to be added so the override actually flows through end-to-end.

Holding the merge until it's out of draft.