Fix HCSpellList lookup for hardcore trainer skip

[FailMaven]

Summary

• Convert HCSpellList from array syntax to keyed [spellId] = true entries so HCSpellList[spellId] lookups in ProcessSpells actually work
• Add Soulstone rank 1 (693) to the hardcore skip list (trained at level 18)

Context

v4.10.13 (c50dc0b) switched hardcore trainer logic to C_GameRules.IsHardcoreActive(), but HCSpellList in DB/classic/spells.lua was unchanged. Entries like 20752, are stored at numeric indices 1..n, not as keys — so HCSpellList[20752] was always nil and listed spells were still auto-purchased on HC servers.

Test plan

• On a Hardcore Classic Era warlock with trainer automation enabled, open a class trainer at level 18+ and confirm Soulstone (693) is not auto-bought
• At level 30+, confirm Create Soulstone ranks (20752+) are not auto-bought
• On a non-HC server (or with trainer automation off), confirm normal trainer behavior is unchanged
• Confirm Hellfire / Reincarnation skips still work on HC

[nicaodl2]

Hey. Why would you not train this? Hellfire is definitely used in HC.

[FailMaven]

It's what was there originally. I only fixed the issues with the spells not actually being flagged (and added R1 ss). Tho to be fair, I'd never use Hellfire in hardcore. It's too scary to me, ha ha