feat: integrate ChaffGames FPS template as local player controller

Replaces the overhead box-mesh view with a full FPS character:

- mouse look, WASD movement, jump (Space), crouch (C), sprint (Shift), lean (Q/E)

- 6 weapons (LMB shoot, R reload, scroll switch, F melee, G drop)

- Crosshair HUD, ammo counter, sprint bar

- Client sends position to server at 20Hz for multiplayer visibility

- Server broadcasts positions to all peers

- Remote players shown as boxes (placeholder)

source: https://godotengine.org/asset-library/asset/2652 (MIT license)

client/template/Spawnable_Objects/Projectiles_To_Load/shotgun_projectile.tscn

@@ -0,0 +1,17 @@
+[gd_scene load_steps=3 format=3 uid="uid://brvfyahytwd8m"]
+
+[ext_resource type="Script" uid="uid://dnh4a4vkl0cl1" path="res://client/template/scripts/Projectiles/shotgun_projectile.gd" id="1_idx2q"]
+
+[sub_resource type="Curve2D" id="Curve2D_2lhxk"]
+_data = {
+"points": PackedVector2Array(0, 0, 0, 0, 7, 3, 0, 0, 0, 0, -30, -11, 0, 0, 0, 0, -8, -18, 0, 0, 0, 0, 8, -9, -2.50282, -11.0124, 2.50282, 11.0124, 19, 13, 0, 0, 0, 0, -21, 1, 0, 0, 0, 0, 22, 22, 0, 0, 0, 0, 12, 21, 0, 0, 0, 0, -33, 4)
+}
+point_count = 9
+
+[node name="shotgun_projectile" type="Node3D"]
+script = ExtResource("1_idx2q")
+Randomness = 2.941
+Split_Damage = true
+
+[node name="shotgun_pattern" type="Path2D" parent="."]
+curve = SubResource("Curve2D_2lhxk")