Improves scene lighting and tree collision

Moves light direction to global shader parameter, enabling dynamic light updates.

Adjusts tree collision shape for better player interaction.

Updates default season to summer.

Common/shaders/outline.gdshader

@@ -13,7 +13,7 @@ uniform float darken_amount : hint_range(0, 1, 0.01) = 0.3;
 uniform float lighten_amount : hint_range(0, 10, 0.01) = 1.5;
 
 uniform vec3 normal_edge_bias = vec3(1, 1, 1);
-uniform vec3 light_direction = vec3(-0.96, -0.18, 0.2);
+global uniform vec3 light_direction;
 
 float get_depth(vec2 screen_uv, mat4 inv_projection_matrix) {
 	float depth = texture(depth_texture, screen_uv).r;