Run dijkstra in the background

[lukacslacko]

Trying to connect two cities while dijkstra is running will be dropped (not completely silently, it will be printed on the console).

[Copilot]

Pull Request Overview

This PR implements running the dijkstra algorithm in the background, ensuring that connecting two cities while the algorithm is busy will be dropped with an appropriate console message. Key changes include:

• Spawning a background thread to execute dijkstra and communicating via a channel.
• Refactoring state management for globe points to use Arc<RwLock<…>> for safe concurrent access.
• Updating system registration and function signatures to integrate the new background computation.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/ui.rs	Adds background dijkstra execution and adjusts system chaining and globe points locking.
src/state.rs	Updates globe points to use Arc<RwLock> for concurrent access.

Comments suppressed due to low confidence (2)

src/ui.rs:54

• The function name 'create_path_if_dijsktra_ready' appears to have a typo. Consider renaming it to 'create_path_if_dijkstra_ready' for consistency.

.add_systems(Update, create_path_if_dijsktra_ready)

src/ui.rs:468

• The variable 'dijksta_communication' is misspelled; renaming it to 'dijkstra_communication' would improve clarity and consistency with its type.

mut dijksta_communication: ResMut<DijkstraCommunication>,