Add restart button to game over screen

[wannerdev]

Description

Adds a restart button to the game over screen that allows players to quickly start a new game without refreshing.

Changes

• Added component
• Implemented system with hover effects
• Button resets score (energy_rate to 0.0, energy_stored to 500.0)
• Transitions back to gameplay screen on click
• Styled to match existing game UI theme with retro aesthetic

Testing

• Button appears at the bottom of the game over popup
• Hover effect changes background color
• Click resets game state and returns to gameplay

Related Issue

Fixes: Hard Mode Challenges - Restart button in game over screen

[wannerdev]

Found multiple attractors in world but n-body physics is not supported: bevy_ecs::system::query::Query<(&ldjam58::physics::directional_forces::Mass, &bevy_transform::components::transform::Transform), ((bevy_ecs::query::filter::Withldjam58::physics::calc_gravity::Attractor, bevy_ecs::query::filter::Withoutldjam58::physics::calc_gravity::Attractee), bevy_ecs::query::filter::Without<ldjam58::physics::directional_forces::GravityForce

the sun needs to be deleted before it can be spawned again!