Implements procedural ground tile generation

Adds procedural ground tile generation with chunking for improved performance.

Includes:
- Ground tile entity with debug text and cell information
- Grass and tree placement based on cell data
- Ground shader for visual representation
- Chunk loading and unloading system based on player position

Entities/GroundTile/GroundTile.gdshader

@@ -0,0 +1,16 @@
+shader_type spatial;
+
+uniform sampler2D noise_texture : filter_linear_mipmap;
+uniform sampler2D gradient_texture : filter_linear;
+uniform float noise_scale : hint_range(0.1, 10.0) = 1.0;
+uniform float roughness_value : hint_range(0.0, 1.0) = 0.8;
+
+void fragment() {
+    vec2 noise_uv = UV * noise_scale;
+    float noise_val = texture(noise_texture, noise_uv).r;
+    
+    vec4 earth_color = texture(gradient_texture, vec2(noise_val, 0.0));
+    
+    ALBEDO = earth_color.rgb;
+    ROUGHNESS = roughness_value;
+}