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

[ikostan]

Description:
Convert fuel-related hard-coded values in player.gd (e.g., max_fuel=100.0, consumption_rate) to a Godot Resource for easier modularity and balancing.

Why is this useful?

• Learning Godot: Demonstrates Resource usage for configurable data.
• Extensibility: Simplifies tweaking values without code changes.
• Balancing: Enables runtime or editor-based adjustments.

Proposed Implementation:

1. Create FuelConfig.tres with fields: max_fuel (100.0), consumption_rate (1.0), thresholds (90/50/30/15%).
2. Load resource in Player.gd _ready(): var fuel_config = load("res://resources/FuelConfig.tres").
   The FuelConfig concept was intentionally merged into GameSettingsResource to prevent code fragmentation and simplify the save/load architecture.
3. Replace hard-coded values with fuel_config.max_fuel, etc.
4. Update logic to emit signals on changes.

Additional Context:
Aligns with signal enhancements; supports future power-ups.