Fix secret-string taint error on aura sourceUnit compare

[hausec]

Summary

Fixes a runtime Lua error on Retail (Midnight secure-aura API) when a non-player aura passes through the blizzard-cooldowns path in AuraButtonOnShow:

attempt to compare local 'sourceUnit' (a secret string value tainted by 'TPerl_PlayerBuffs')

auraData.sourceUnit from C_UnitAuras.GetAuraDataByIndex is sometimes returned as a "secret" (tainted) string that throws when compared directly with ==. The error can fire hundreds of times per second while any such aura is visible.

Change

In TPerl/TPerl.lua AuraButtonOnShow:

• Also capture isFromPlayerOrPlayerPet from auraData (the boolean replacement for the == "player" heuristic).
• Compute isPlayerSource safely: prefer isFromPlayerOrPlayerPet when accessible; fall back to the old sourceUnit == "player" compare only after TPerl_CanAccess(sourceUnit) confirms the value isn't secret; default to false otherwise.
• Pass the resulting boolean to TPerl_CooldownFrame_SetTimer in place of the raw compare.

Net diff is 12 additions / 2 deletions, all inside one function. The classic UnitAura path is untouched.

Test plan

• Retail: reload with a non-player HoT/buff active on the player frame (e.g. a priest PW:S from a raid healer) — error no longer fires.
• Retail: player-cast buffs still get the cooldown swipe + countdown text (i.e. isPlayerSource still resolves to true via isFromPlayerOrPlayerPet).
• Classic: path is unchanged; UnitAura returns a plain string for sourceUnit and takes the old comparison branch.