fix: PluginLayer error boundary and map safety checks

[accius]

• Wrap each PluginLayer in its own error boundary so a single crashed plugin (getPane().appendChild on a dead map) never takes down the whole dashboard. Boundary auto-resets on projection switch.
• Add isMapAlive() guard: validates map._container and _panes exist before passing to hooks — prevents effects from using destroyed maps.
• PluginLayer key now includes projection (az/merc) so hooks fully remount with clean refs when switching map instances.
• useCityLights: fall back to default pane when nightPane doesn't exist on the azimuthal map.
• Reject legacy 'azimuthal' mapStyle from localStorage.

What does this PR do?

Type of change

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

How to test

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)