fix: add missing enchantment effects for rotTouch, soulRend, master, and legendary spells

- Add spell_rotTouch to BASIC_SPELL_EFFECTS (death element Tier 1)
- Add spell_soulRend to TIER2_SPELL_EFFECTS (death element Tier 2)
- Add spell_cosmicStorm, spell_heavenLight, spell_oblivion, spell_deathMark to TIER3_SPELL_EFFECTS (master spells)
- Create legendary-spells.ts with spell_stellarNova, spell_voidCollapse, spell_crystalShatter (legendary spells)
- Update spell-effects/index.ts to include LEGENDARY_SPELL_EFFECTS in SPELL_EFFECTS

Closes #41

src/lib/game/data/enchantments/spell-effects/tier2-spells.ts

@@ -126,4 +126,14 @@ export const TIER2_SPELL_EFFECTS: Record<string, EnchantmentEffectDef> = {
     allowedEquipmentCategories: ALL_CASTER,
     effect: { type: 'spell', spellId: 'shadowStorm' }
   },
+  spell_soulRend: {
+    id: 'spell_soulRend',
+    name: 'Soul Rend',
+    description: 'Grants the ability to cast Soul Rend (50 death damage)',
+    category: 'spell',
+    baseCapacityCost: 170,
+    maxStacks: 1,
+    allowedEquipmentCategories: ALL_CASTER,
+    effect: { type: 'spell', spellId: 'soulRend' }
+  },
 };