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)

client/map_template/assets/prefabs/bomb_site.tscn

@@ -0,0 +1,36 @@
+[gd_scene load_steps=4 format=3]
+
+[sub_resource type="StandardMaterial3D" id="SiteMat"]
+albedo_color = Color(1.0, 0.65, 0.0, 0.3)
+metallic = 0.0
+roughness = 0.5
+transparency = 0.7
+flags_transparent = true
+
+[sub_resource type="BoxShape3D" id="SiteShape"]
+size = Vector3(6.0, 3.0, 6.0)
+
+[node name="BombSite" type="Area3D"]
+groups = ["bomb_site"]
+; Bomb site — the bomb can be planted within this area.
+; Resize the CollisionShape3D to cover the site's playable area.
+; Name the node "BombsiteA" or "BombsiteB" for game logic identification.
+
+[node name="CollisionShape3D" type="CollisionShape3D" parent="."]
+shape = SubResource("SiteShape")
+
+[node name="Visualizer" type="CSGBox3D" parent="."]
+size = Vector3(6.0, 0.04, 6.0)
+material = SubResource("SiteMat")
+use_collision = false
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0.02, 0)
+; Semi-transparent orange floor panel to visualise the site in the editor.
+; Adjust to match the site's floor area.
+
+[node name="PlaneZone" type="CSGBox3D" parent="BombSite"]
+operation = 1
+size = Vector3(5.5, 0.5, 5.5)
+material = SubResource("SiteMat")
+use_collision = false
+transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0)
+; Invisible CSG subtraction hint — marks the plantable ground area.