Visual overhaul: theme, illustrations, redesigned screens (0.3.0)

Phase "habillage" of the post-0.1.0 plan. Rendering was reviewed on real
screenshots (new tools/screenshot.gd, `make screenshot`), which also
caught and fixed map markers overlapping and truncated titles.

- Global Godot theme (Atkinson Hyperlegible font, cream/green/gold
  palette, raised buttons, rounded cards, thick keyboard focus).
- Original vector art: forest/marsh backdrops, Plume the owl, stars,
  exercise-type icons, correct/try-again icons, 10 collection items.
- Redesigned world map (markers as cards with icon, title and stars,
  responsive layout), profile screens, mission intro, exercise host,
  rule/feedback panels, reward screen and collection grid.
- Motion helper (pop-in, fade) honouring an animations setting.
- Settings: animations flag; base window 1152x648 with canvas_items.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

scenes/world/world_map.tscn

@@ -1,7 +1,9 @@
-[gd_scene load_steps=3 format=3]
+[gd_scene load_steps=5 format=3]
 
 [ext_resource type="Script" path="res://scenes/world/world_map.gd" id="1"]
 [ext_resource type="PackedScene" path="res://scenes/characters/guide_owl.tscn" id="2"]
+[ext_resource type="PackedScene" path="res://scenes/ui/backdrop.tscn" id="backdrop"]
+[ext_resource type="Texture2D" path="res://assets/interface/star_full.svg" id="3"]
 
 [node name="WorldMap" type="Control"]
 layout_mode = 3
@@ -12,55 +14,89 @@ grow_horizontal = 2
 grow_vertical = 2
 script = ExtResource("1")
 
-[node name="Background" type="ColorRect" parent="."]
+[node name="Backdrop" parent="." instance=ExtResource("backdrop")]
+unique_name_in_owner = true
 layout_mode = 1
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
 grow_horizontal = 2
 grow_vertical = 2
-color = Color(0.3, 0.52, 0.33, 1)
 
-[node name="VBox" type="VBoxContainer" parent="."]
+[node name="Margin" type="MarginContainer" parent="."]
 layout_mode = 1
 anchors_preset = 15
 anchor_right = 1.0
 anchor_bottom = 1.0
 grow_horizontal = 2
 grow_vertical = 2
+theme_override_constants/margin_left = 20
+theme_override_constants/margin_top = 14
+theme_override_constants/margin_right = 20
+theme_override_constants/margin_bottom = 10
+
+[node name="VBox" type="VBoxContainer" parent="Margin"]
+layout_mode = 2
+theme_override_constants/separation = 8
+
+[node name="TopBar" type="HBoxContainer" parent="Margin/VBox"]
+layout_mode = 2
 theme_override_constants/separation = 12
 
-[node name="TitleLabel" type="Label" parent="VBox"]
+[node name="ProfileButton" type="Button" parent="Margin/VBox/TopBar"]
 unique_name_in_owner = true
+theme_type_variation = &"SecondaryButton"
 layout_mode = 2
-theme_override_font_sizes/font_size = 32
+custom_minimum_size = Vector2(0, 52)
+
+[node name="TitleLabel" type="Label" parent="Margin/VBox/TopBar"]
+unique_name_in_owner = true
+theme_type_variation = &"HeaderTitle"
+layout_mode = 2
+size_flags_horizontal = 3
 horizontal_alignment = 1
 
-[node name="TotalStarsLabel" type="Label" parent="VBox"]
+[node name="StarsBadge" type="PanelContainer" parent="Margin/VBox/TopBar"]
+theme_type_variation = &"Pill"
+layout_mode = 2
+
+[node name="Row" type="HBoxContainer" parent="Margin/VBox/TopBar/StarsBadge"]
+layout_mode = 2
+
+[node name="StarIcon" type="TextureRect" parent="Margin/VBox/TopBar/StarsBadge/Row"]
+layout_mode = 2
+custom_minimum_size = Vector2(34, 34)
+size_flags_vertical = 4
+texture = ExtResource("3")
+expand_mode = 1
+stretch_mode = 5
+
+[node name="TotalStarsLabel" type="Label" parent="Margin/VBox/TopBar/StarsBadge/Row"]
+unique_name_in_owner = true
+theme_type_variation = &"Emphasis"
+layout_mode = 2
+
+[node name="CollectionButton" type="Button" parent="Margin/VBox/TopBar"]
 unique_name_in_owner = true
 layout_mode = 2
-horizontal_alignment = 1
+custom_minimum_size = Vector2(0, 52)
 
-[node name="MapArea" type="Control" parent="VBox"]
+[node name="MapArea" type="Control" parent="Margin/VBox"]
 unique_name_in_owner = true
 layout_mode = 2
 size_flags_vertical = 3
 
-[node name="LevelToggleButton" type="Button" parent="VBox"]
-unique_name_in_owner = true
+[node name="BottomBar" type="HBoxContainer" parent="Margin/VBox"]
 layout_mode = 2
-custom_minimum_size = Vector2(0, 48)
+theme_override_constants/separation = 12
 
-[node name="CollectionButton" type="Button" parent="VBox"]
+[node name="Guide" type="Control" parent="Margin/VBox/BottomBar" instance=ExtResource("2")]
 unique_name_in_owner = true
 layout_mode = 2
-custom_minimum_size = Vector2(0, 48)
 
-[node name="ProfileButton" type="Button" parent="VBox"]
-unique_name_in_owner = true
-layout_mode = 2
-custom_minimum_size = Vector2(0, 48)
-
-[node name="Guide" type="Control" parent="VBox" instance=ExtResource("2")]
+[node name="LevelToggleButton" type="Button" parent="Margin/VBox/BottomBar"]
 unique_name_in_owner = true
+theme_type_variation = &"SecondaryButton"
 layout_mode = 2
+size_flags_vertical = 4
+custom_minimum_size = Vector2(0, 52)