Elementals Connector Compat Skill Tree Fix

Built from:
- elementals-1.48.6-geckolib-forge-4.8.4-connector-compat-server-nbt-bootstrap-wisp(1).jar
- source sha256: bf9a0fb3fba6002c7ad62141832c06fda92b816b6b884b215a88b80da719f943

Patch source for restored packets:
- elementals-1.48.6-geckolib-forge-4.8.4-connector-compat-mp-nbtfix.jar
- donor sha256: 2eee893bd2aaf1de4917fbdfef6492b5398095f2c6b0d39907e83d710fcb4f8c

What was wrong:
- The server-nbt-bootstrap-wisp build had the upgrade-list sync packets no-oped:
  - GetUpgradeListC2SPacket.receive/send returned immediately
  - SyncUpgradeListS2CPacket.receive/send returned immediately
- That stopped the skill tree from requesting and receiving upgrade data.

What changed:
- Restored the multiplayer-safe, null-guarded upgrade-list packet classes:
  - dev/saperate/elementals/network/packets/GetUpgradeListC2SPacket.class
  - dev/saperate/elementals/packets/SyncUpgradeListS2CPacket.class

What did not change:
- No Elementals features were removed.
- Fire Wisp functions remain.
- GeckoLib Forge compatibility remains.
- Server NBT bootstrap fix remains.
- No external dependency jars were modified.

Expected result:
- Skill tree can request upgrade data again.
- Buying/toggling upgrades can sync back to the client again.
- NBT null crash protection remains in the server state/bootstrap code.
