Phase 7: netfox + godot-jolt stack upgrade

Stack installed:
- netfox v1.35.3 (core + extras + noray + internals)
- godot-jolt v0.16.0-stable

Architecture:
- Server: ENet transport (works headless, no netfox deps)
- Client/Editor: netfox rollback (RollbackSynchronizer, TickInterpolator)

New/modified:
- docs/migration-netfox-plan.md — migration architecture
- scripts/network/network_manager.gd — netfox-aware ENet fallback
- scripts/network/player.gd — clean base player
- client/characters/player_netfox.gd — rollback player w/ WeaponManager
- client/characters/input/player_net_input.gd — BaseNetInput subclass
- client/characters/character/fps_character_controller.gd — netfox input feed
- client/weapons/ — weapon data, registry, TacticalWeaponHitscan, WeaponManager
- client/scripts/round_replicator.gd — client-side round state bridge
- server/scripts/round_manager.gd — improved state machine
- server/scripts/plugin_api/plugin_manager.gd — refined plugin system
- config: enemy_tag, ally_tag for meatball targeting

Removed: old C++ SimulationServer GDExtension (replaced by netfox rollback)

server/server-browser-api/venv/lib/python3.11/site-packages/websockets/utils.py

@@ -0,0 +1,53 @@
+from __future__ import annotations
+
+import base64
+import hashlib
+import secrets
+import sys
+
+from .typing import BytesLike
+
+
+__all__ = ["accept_key", "apply_mask"]
+
+
+GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"
+
+
+def generate_key() -> str:
+    """
+    Generate a random key for the Sec-WebSocket-Key header.
+
+    """
+    key = secrets.token_bytes(16)
+    return base64.b64encode(key).decode()
+
+
+def accept_key(key: str) -> str:
+    """
+    Compute the value of the Sec-WebSocket-Accept header.
+
+    Args:
+        key: Value of the Sec-WebSocket-Key header.
+
+    """
+    sha1 = hashlib.sha1((key + GUID).encode()).digest()
+    return base64.b64encode(sha1).decode()
+
+
+def apply_mask(data: BytesLike, mask: bytes | bytearray) -> bytes:
+    """
+    Apply masking to the data of a WebSocket message.
+
+    Args:
+        data: Data to mask.
+        mask: 4-bytes mask.
+
+    """
+    if len(mask) != 4:
+        raise ValueError("mask must contain 4 bytes")
+
+    data_int = int.from_bytes(data, sys.byteorder)
+    mask_repeated = mask * (len(data) // 4) + mask[: len(data) % 4]
+    mask_int = int.from_bytes(mask_repeated, sys.byteorder)
+    return (data_int ^ mask_int).to_bytes(len(data), sys.byteorder)