Prevent blown-up vehicles from spawning excess flying components

[Lpsd]

Summary

Prevent blown-up vehicles from spawning excess flying components through the damage sync layer, by adding IsBlown guards across all paths that propagate damage state changes.

This is a defense-in-depth fix. The triggering scenario for issue #4916 is resolved at the source by PR #4966 (which prevents blown aircraft from re-entering STATUS_PHYSICS). These sync-layer guards enforce that a destroyed vehicle should never spawn flying components or sync damage, protecting against any future path that might trigger damage on a wreck.

The initial blow damage reaches all clients through PACKET_ID_EXPLOSION or the BLOW_VEHICLE RPC - both call FuckCarCompletely locally on every client; SyncDamageModel is never involved in the initial state, so the IsBlown guard only blocks subsequent re-syncs.

Motivation

Fixes, in combination with #4966, issue #4916.

Without #4966: a blown plane stuck in STATUS_PHYSICS produces GTA-native flying components locally on contact. This PR ensures that even if those damage events occur, they are not propagated to other clients where they would cause additional spawns.

Without this PR: if any code path (a Lua event, a new special property, a GTA edge case) ever triggers panel damage on a blown vehicle, every client receives the sync and spawns a full set of flying components. These guards prevent that class of bug permanently.

Changes:

• CDeathmatchVehicle::SyncDamageModel: skip the entire sync if the vehicle is blown; no packet is sent
• Server CGame::Packet_VehicleDamageSync: ignore incoming damage syncs for blown vehicles; do not broadcast
• CNetAPI::ReadVehiclePartsState: suppress flying component spawns when applying damage to a blown vehicle
• CPacketHandler (two sites receiving damage syncs): same IsBlown guard on the flyingComponents flag

No bitstream format changes. The guards are purely behavioral.

Test plan

1. Start a server with vehicle_engine_autostart disabled
2. Spawn a Dodo, blow it up, walk into the wreckage
3. Verify no cascading flying components or explosions appear (requires Fix repeated aircraft wreck components when engine autostart is disabled #4966)
   4

Checklist

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