Exiles Reach: implement Giant Boar Trample (305557)

The trample's Effect 1 is a SPELL_EFFECT_DUMMY (radius 13, targets the
caster) that was never scripted, so it did nothing to the Monstrous
Cadavers (157091) during Ride of the Scientifically Enhanced Boar. Add a
spell script that damages all hostile creatures within the effect radius
(caster->DealDamage, effect value). Registered + spell_script_names row.

src/server/scripts/ExilesReach/exiles_reach_darkmaul_plains.cpp

@@ -22,6 +22,9 @@
  */
 
 #include "exiles_reach.h"
+#include "CellImpl.h"
+#include "GridNotifiers.h"
+#include "GridNotifiersImpl.h"
 
 class exiles_reach_darkmaul_plains_playerscript : public PlayerScript
 {
@@ -982,6 +985,50 @@ public:
     }
 };
 
+// Giant Boar Trample (305557) — mows down the undead army / Monstrous Cadavers
+// (157091) around the boar. The spell's Effect 1 is a DUMMY (radius 13) that
+// targets the caster; the actual damage to nearby enemies is scripted here.
+class spell_giant_boar_trample_305557 : public SpellScriptLoader
+{
+public:
+    spell_giant_boar_trample_305557() : SpellScriptLoader("spell_giant_boar_trample_305557") {}
+
+    class spell_giant_boar_trample_305557_SpellScript : public SpellScript
+    {
+        void HandleDummy(SpellEffIndex /*effIndex*/)
+        {
+            Unit* caster = GetCaster();
+            if (!caster || !caster->IsInWorld())
+                return;
+
+            float radius = GetEffectInfo().CalcRadius(caster);
+            int32 damage = GetEffectValue();
+
+            std::list<Creature*> targets;
+            Trinity::AnyUnitInObjectRangeCheck u_check(caster, radius);
+            Trinity::CreatureListSearcher<Trinity::AnyUnitInObjectRangeCheck> searcher(caster, targets, u_check);
+            Cell::VisitGridObjects(caster, searcher, radius);
+
+            for (Creature* target : targets)
+            {
+                if (!caster->IsValidAttackTarget(target))
+                    continue;
+                caster->DealDamage(target, damage, nullptr, DIRECT_DAMAGE, SPELL_SCHOOL_MASK_NORMAL);
+            }
+        }
+
+        void Register() override
+        {
+            OnEffectHit += SpellEffectFn(spell_giant_boar_trample_305557_SpellScript::HandleDummy, EFFECT_1, SPELL_EFFECT_DUMMY);
+        }
+    };
+
+    SpellScript* GetSpellScript() const override
+    {
+        return new spell_giant_boar_trample_305557_SpellScript();
+    }
+};
+
 class LeaveGiantBoarEvent : public BasicEvent
 {
 public:
@@ -1086,4 +1133,5 @@ void AddSC_exiles_reach_darkmaul_plains()
     new spell_ride_vehicle_173426();
     new spell_giant_boar_charge_321627();
     new spell_giant_boar_ping_vehicle_305559();
+    new spell_giant_boar_trample_305557();
 }