t_p2: Add team, spawn, and buy-zone system

- team_data.gd: Team enum (SPECTATOR/CT/Terrorist), constants for names,
  colors, starting money, and spawn groups; TeamData resource class
- team_manager.gd: Player-to-team assignment, auto-balancing, score
  tracking; round-independent (persists across rounds)
- spawn_manager.gd: Scans scene for Marker3D nodes in spawn_points_ct
  and spawn_points_t groups; selects valid spawns (farthest from enemies
  with proximity check, fallback to first available)
- buy_zone.gd: Area3D-based trigger zone with team filtering, player
  enter/exit tracking and signals
- test_range.tscn: Added 2 CT spawn markers and 2 T spawn markers with
  appropriate groups

server/scripts/zones/buy_zone.gd

@@ -0,0 +1,181 @@
+## BuyZone — Area3D that defines where players can buy weapons/equipment.
+##
+## A trigger zone that tracks which players are inside it and emits
+## enter/exit signals. Buy zones can be filtered by team, so only
+## the appropriate team can purchase within a given zone.
+##
+## In the map scene, place BuyZone nodes (Area3D) near each team's
+## spawn area. Set zone_team to restrict which team can use it.
+##
+## Usage (map tscn):
+##   [node name="BuyZone_CT" type="Area3D" parent="."]
+##   script = ExtResource("...buy_zone.gd")
+##   zone_team = 1          # Team.COUNTER_TERRORIST
+##   zone_radius = 10.0
+##
+##   (Add a CollisionShape3D child with a SphereShape3D for the trigger volume.)
+##
+## Signals:
+##   player_entered_buyzone(player_id) — emitted when a player enters the zone
+##   player_exited_buyzone(player_id)  — emitted when a player leaves the zone
+##
+## Usage (server runtime):
+##   var bz: BuyZone = $BuyZone_CT
+##   if bz.is_in_buyzone(player_id):
+##       show_buy_menu(player_id)
+
+extends Area3D
+class_name BuyZone
+
+# ---------------------------------------------------------------------------
+# Signals
+# ---------------------------------------------------------------------------
+
+## Emitted when a player enters the buy zone.
+signal player_entered_buyzone(player_id: int)
+
+## Emitted when a player exits the buy zone.
+signal player_exited_buyzone(player_id: int)
+
+
+# ---------------------------------------------------------------------------
+# Exports
+# ---------------------------------------------------------------------------
+
+## Which team(s) can use this buy zone.
+## Team.COUNTER_TERRORIST = 1, Team.TERRORIST = 2, Team.SPECTATOR = 0.
+## Use the Team enum: TeamData.Team.COUNTER_TERRORIST, etc.
+@export var zone_team: TeamData.Team = TeamData.Team.COUNTER_TERRORIST
+
+## Radius of the buy zone in Godot units (visual hint only; actual collision
+## shape determines the trigger volume).
+@export var zone_radius: float = 10.0
+
+## If true, any team can use this zone (overrides zone_team).
+@export var allow_all_teams: bool = false
+
+
+# ---------------------------------------------------------------------------
+# State
+# ---------------------------------------------------------------------------
+
+## Set of player IDs currently inside this buy zone.
+var _players_in_zone: Dictionary = {}  # player_id (int) → true
+
+
+# ---------------------------------------------------------------------------
+# Lifecycle
+# ---------------------------------------------------------------------------
+
+func _ready() -> void:
+	# Connect area signals
+	body_entered.connect(_on_body_entered)
+	body_exited.connect(_on_body_exited)
+	area_entered.connect(_on_area_entered)
+	area_exited.connect(_on_area_exited)
+
+	# Set collision layer/mask for buy zones (layer 4 by convention)
+	collision_layer = 0  # Buy zones don't collide with physics
+	collision_mask = 0   # They detect bodies via signals only
+
+	# Ensure we have at least a basic collision shape hint
+	_setup_collision_shape()
+
+
+# ---------------------------------------------------------------------------
+# Public API
+# ---------------------------------------------------------------------------
+
+## Check if a specific player is inside this buy zone.
+func is_in_buyzone(player_id: int) -> bool:
+	return _players_in_zone.has(player_id)
+
+
+## Get an array of player IDs currently inside this buy zone.
+func get_players_in_buyzone() -> Array[int]:
+	return _players_in_zone.keys()
+
+
+## Check if the given team is allowed to use this buy zone.
+func is_team_allowed(team: TeamData.Team) -> bool:
+	if allow_all_teams:
+		return true
+	return team == zone_team
+
+
+## Get the number of players currently in the zone.
+func get_player_count() -> int:
+	return _players_in_zone.size()
+
+
+# ---------------------------------------------------------------------------
+# Internal: Signal handlers
+# ---------------------------------------------------------------------------
+
+func _on_body_entered(body: Node) -> void:
+	var player_id: int = _extract_player_id(body)
+	if player_id >= 0:
+		_players_in_zone[player_id] = true
+		player_entered_buyzone.emit(player_id)
+
+
+func _on_body_exited(body: Node) -> void:
+	var player_id: int = _extract_player_id(body)
+	if player_id >= 0 and _players_in_zone.erase(player_id):
+		player_exited_buyzone.emit(player_id)
+
+
+func _on_area_entered(_area: Area3D) -> void:
+	# Areas can also trigger if the player is an Area3D (e.g. a trigger zone
+	# on the player). For now, body detection is the primary path.
+	pass
+
+
+func _on_area_exited(_area: Area3D) -> void:
+	pass
+
+
+# ---------------------------------------------------------------------------
+# Internal: helpers
+# ---------------------------------------------------------------------------
+
+## Try to extract a multiplayer peer ID from a body node.
+## The body is expected to be a Player node or have a "get_peer_id" method,
+## or the body's owner is a Player node with multiplayer authority info.
+func _extract_player_id(body: Node) -> int:
+	# If the body has a peer_id property or method
+	if body.has_method(&"get_peer_id"):
+		return body.get_peer_id()
+
+	# If the body is a Player node with multiplayer authority
+	if body.has_method(&"get_multiplayer_authority"):
+		return body.get_multiplayer_authority()
+
+	# Check for a direct peer_id variable
+	if "peer_id" in body and body.get("peer_id") is int:
+		return body.get("peer_id")
+
+	# Try the body's owner
+	var owner_node: Node = body.owner if body.owner else body.get_parent()
+	if owner_node and owner_node != body:
+		return _extract_player_id(owner_node)
+
+	return -1
+
+
+## Ensure there's a collision shape for the trigger volume.
+## If no CollisionShape3D child exists, create a SphereShape3D one.
+func _setup_collision_shape() -> void:
+	# Check if we already have a CollisionShape3D
+	for child in get_children():
+		if child is CollisionShape3D:
+			return  # Already have one
+
+	# Create a default sphere shape
+	var shape := SphereShape3D.new()
+	shape.radius = zone_radius
+
+	var col_shape := CollisionShape3D.new()
+	col_shape.shape = shape
+	add_child(col_shape)
+	col_shape.owner = get_tree().edited_scene_root if Engine.is_editor_hint() else owner