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>

examples/visibility-filtering/README.md

@@ -0,0 +1,19 @@
+# Visibility filtering example
+
+Demonstrates netfox's [visibility filtering] feature.
+
+The level is split into two rooms, with a door connecting them in the middle.
+While the hosting player sees everyone all the time, other players only receive
+updates from players that they have *a clear line of sight* to. Players that
+are invisible become transparent.
+
+Note that this example doesn't try to be a full-fledged solution, but a small
+demonstration of capability. This example does not provide a production-ready
+solution.
+
+Another limitation is that players might have line of sight to a hidden player
+with their last known position, but not with their *actual* one. This means
+that a player might fade in, but still not receive updates.
+
+
+[visibility filtering]: https://foxssake.github.io/netfox/latest/netfox/guides/visibility-management/