[FEATURE] Convert Hard-Coded Speed Elements to Godot Resource

[ikostan]

Description:
Implement a dynamic ParallaxBackground system that automatically adjusts its scrolling speed based on the player's current forward velocity.

(Note to automated reviewers: Previous draft requirements involving a standalone SpeedConfig resource have been superseded. Global speed and fuel constraints were already successfully implemented via GameSettingsResource in PR #542. This issue is strictly scoped to the Parallax visual implementation).

Acceptance Criteria:

• Create a parallax_manager.gd script that extends ParallaxBackground.
• Implement an observer method (_on_player_speed_changed) in the Parallax Manager to cache the broadcasted speed.
• In the main scene script (main_scene.gd), dynamically connect the Player's speed_changed signal to the Parallax Manager.
• Update the scroll_offset.y in the _process loop of the Parallax Manager based on the cached speed.
• Remove direct physics/fuel polling from main_scene.gd to prove true architectural decoupling.

Why is this useful? * Visual Feedback: Gives the player a much stronger sense of momentum and speed.

• Architecture: Proves the success of the decoupling work done in [FEATURE] Add Signals for Speed Controls in Player.gd #279, demonstrating that external environmental systems can safely listen to player physics.