feat: strengthen water and foreground silhouettes

- Upgrade river shader with multi-layer UV flow, fresnel edges, foam highlights, and specular sparkle
- Upgrade waterfall shader with dual-band scrolling, distinct foam contrast, and rim transparency
- Widen river (8m) and waterfall (8m) for greater visual presence
- Increase waterfall mist particles to 72 with wider spread and longer lifetime
- Add fortress crenellations (10), three turrets, and prominent ridge banner for readable skyline silhouette
- Remove duplicate banner nodes from JajceWorld instance (now owned by FortressBlockout scene)
- Update BUILD_IN_PUBLIC_PLAN and LEARNING_ROADMAP to reflect completion

world/jajce/WaterfallMist.tscn

@@ -1,19 +1,19 @@
 [gd_scene load_steps=4 format=3]
 
 [sub_resource type="ParticleProcessMaterial" id="ParticleProcessMaterial_mist"]
-lifetime_randomness = 0.2
+lifetime_randomness = 0.35
 spread = 180.0
-gravity = Vector3(0, -0.5, 0)
-initial_velocity_min = 0.3
-initial_velocity_max = 0.8
-scale_min = 0.1
-scale_max = 1.5
-color = Color(0.85, 0.95, 0.95, 0.4)
+gravity = Vector3(0, -0.35, 0)
+initial_velocity_min = 0.25
+initial_velocity_max = 1.2
+scale_min = 0.08
+scale_max = 2.0
+color = Color(0.82, 0.94, 0.96, 0.35)
 emission_shape = 1
-emission_box_extents = Vector3(2.5, 1.0, 0.5)
+emission_box_extents = Vector3(4.5, 1.5, 1.0)
 
 [sub_resource type="StandardMaterial3D" id="Material_mist"]
-albedo_color = Color(0.85, 0.95, 0.95, 0.35)
+albedo_color = Color(0.82, 0.94, 0.96, 0.28)
 transparency = 1
 shading_mode = 0
 billboard_mode = 1
@@ -21,14 +21,14 @@ cull_mode = 0
 
 [sub_resource type="QuadMesh" id="Mesh_mist"]
 material = SubResource("Material_mist")
-size = Vector2(1.5, 1.5)
+size = Vector2(1.8, 1.8)
 
 [node name="WaterfallMist" type="GPUParticles3D"]
 emitting = true
-amount = 48
-lifetime = 2.5
+amount = 72
+lifetime = 3.0
 one_shot = false
-preprocess = 1.0
+preprocess = 1.5
 speed_scale = 1.0
 local_coords = true
 draw_order = 0