Fresh start: replace with naxIO/netfox-cs-sample foundation

Complete replacement of the tactical-shooter project with the
netfox-cs-sample (MIT) — a CS 1.6 inspired multiplayer FPS built
with Godot 4 and netfox.

## What's new
- Full CS-style gameplay: teams (T/CT), rounds, economy, buy menu
- 6 weapons: Knife, Glock, USP, AK-47, M4A1, AWP
- Bomb plant/defuse with 2 bombsites
- Flashbang & smoke grenades
- Proper netfox rollback netcode at 64 tick
- Network popup UI for host/join
- HUD, crosshair, round timer, scoreboard
- All netfox singletons registered as autoloads (works in exported builds)

## Architecture
- Listen-server (host from client, no dedicated server binary)
- Multiplayer-fps game lives at examples/multiplayer-fps/
- Netfox addons registered as autoloads for exported build compat
- Godot 4.7 with Forward+ renderer

## Removed
- Old headless-server architecture (client_main, server_main, player.gd, etc.)
- Custom netfox bootstrap with ENet fallback
- Old ChaffGames FPS template (2,420 lines, 844 KB)
- SimulationServer GDExtension stub
- Godot-jolt physics (netfox sample uses default Godot physics)
- Duplicate weapon_data.gd, anti_cheat.gd, round_manager.gd, etc.
- Server browser API Python venv (87 MB)
- test_range map and modular assets

## Preserved
- Git history
- Server config at config/default_server_config.cfg
- Windows export preset
- Build directory (gitignored)

Co-authored-by: naxIO <naxIO@users.noreply.github.com>

addons/netfox/schemas/network-schema-serializer.gd

@@ -0,0 +1,21 @@
+extends RefCounted
+class_name NetworkSchemaSerializer
+
+## Base class for serializers, to use with [NetworkSchemas]
+##
+## Each serializer must be able to encode and decode values passed to it.
+## Data is stored in [StreamPeerBuffer] objects.
+## [br][br]
+## To implement a custom serializer, extend this class and pass an instance of
+## it in place of a NetworkSchemaSerializer, for example to [method
+## RollbackSynchronizer.set_schema].
+##
+## @tutorial(Network schemas): https://foxssake.github.io/netfox/latest/netfox/guides/network-schemas/
+
+## Encode [param value] into [param buffer]
+func encode(value: Variant, buffer: StreamPeerBuffer) -> void:
+	pass
+
+## Decode a value from [param buffer] and return it
+func decode(buffer: StreamPeerBuffer) -> Variant:
+	return null