feat(playerbots): staggered taxi take-off for bots (#1281)

* feat(playerbots): staggered taxi take-off for bots

Adds four new configurable settings to playerbots.conf:

- AiPlayerbot.BotTaxiDelayMinMs:   Min random delay before the 1st follower bot clicks the flight-master
- AiPlayerbot.BotTaxiDelayMaxMs:   Upper bound for the overall taxi delay window – larger spreads big raids
- AiPlayerbot.BotTaxiGapMs:        Fixed gap added per group-slot so bots never take off together
- AiPlayerbot.BotTaxiGapJitterMs:  Extra small randomness added to each gap so launches don’t look robotic

These options allow server owners to fine-tune how bots queue up and take off from flight masters, making their behavior appear more natural.

Closes #1017 : Bots use Flight master nearly the same time.

* fixed build errors

Was missing a header and variable declarations.

src/PlayerbotAI.h

@@ -590,6 +590,9 @@ public:
     NewRpgStatistic rpgStatistic;
     std::unordered_set<uint32> lowPriorityQuest;
 
+    // Schedules a callback to run once after <delayMs> milliseconds.
+    void AddTimedEvent(std::function<void()> callback, uint32 delayMs);
+
 private:
     static void _fillGearScoreData(Player* player, Item* item, std::vector<uint32>* gearScore, uint32& twoHandScore,
                                    bool mixed = false);