Spells/Warlock: Implement Demonic Gateway - #32054

Changes proposed:

• Implement Demonic Gateway and the AI for both endpoints (59262 and 59271).
• Pair endpoints belonging to the same Warlock and allow the owner and party/raid members to use them. Keep the existing travel spells and usage cooldown.
• Despawn the owner's previous endpoints before creating a new pair. Collect their GUIDs before despawning to avoid invalidating the map-store iterator.
• Despawn endpoints when their owner leaves the world or their partner is removed.
• Add creature, spell-click and spell-script bindings, and regression tests for casting checks, access, replacement, cleanup and cooldown handling.

Issues addressed:

Demonic Gateway currently has no spell implementation or endpoint AI on master. No linked issue.

Tests performed:

• Builds with Clang 18 and MySQL, with warnings treated as errors: worldserver, bnetserver and tests. Minimal dynamic scripts, no PCH.
• All 43 CTests pass. Gateway tests pass 8 cases / 84 assertions, including both travel directions, party access, unrelated-player rejection, replacement and cooldown expiry/reuse.
• AddressSanitizer reproduces a heap-use-after-free with the unsafe replacement loop; the GUID snapshot passes the Gateway tests. Instrumentation covers the spell script and fixture; core libraries are uninstrumented and leak detection is disabled.
• Validated spell effects against client build 12.1.0.69933 using the MySQL hotfix loader. Checked SQL bindings, unrelated-record preservation and repeat application on MySQL temporary tables.
• Owner travel, right-click use, replacement and cooldown expiry/reuse were tested in-game on an earlier revision. The submitted revision has automated validation.

Known issues and TODO list:

• Test the submitted revision in-game: party/raid access, logout cleanup, movement and terrain/line-of-sight restrictions. Confirm the 6-yard height check and endpoint pairing radius against retail.
• Verify Gateway Control Shard, flag carriers and Gateway Mastery interactions.
• Test startup with a clean TDB world database. SQL tests use reference table definitions; local client assets do not include maps/vmaps.
• Review the replacement scan. It traverses the map's creature store because these endpoints have no owner summon slot and are not in the controlled-minion list.

Frequent Traveler is handled separately in #32055. The automated travel fixtures use synthetic spell data and do not test client movement.

Please review endpoint pairing and lifetime, access checks, destination restrictions and database bindings.