Balance-Druid-improve-Starfall-usage-and-add-CC-safety (#1713)

- Move Starfall from default actions to AOE strategy only
- Require 2+ enemies for Starfall usage (prevents single-target casting)
- Add CC safety: avoid casting Starfall near current CC targets
- Prioritize Starfall over Hurricane in medium AOE situations
- Remove Starfall from pull/opener rotation to prevent early
single-target usage

This prevents Balance druids from wasting Starfall on single targets
and breaking crowd control effects in group content.

src/strategy/druid/DruidActions.h

@@ -144,6 +144,8 @@ class CastStarfallAction : public CastSpellAction
 {
 public:
     CastStarfallAction(PlayerbotAI* botAI) : CastSpellAction(botAI, "starfall") {}
+
+    bool isUseful() override;
 };
 
 class CastHurricaneAction : public CastSpellAction