Add comprehensive spell sound manager with 35+ magic sounds

Implemented complete spell casting audio system with all magic schools:

Magic schools supported:
- Fire: Precast (Low/Medium/High), Cast, Fireball impacts
- Frost: Precast (Low/Medium/High), Cast, Blizzard impacts
- Holy: Precast (Low/Medium/High), Cast, Holy impacts (4 levels)
- Nature: Precast (Low/Medium/High), Cast
- Shadow: Precast (Low/Medium/High), Cast
- Arcane: Precast, Arcane Missile impacts
- Physical: Non-magical abilities

Spell phases:
- Precast: Channeling/preparation sounds (before cast)
- Cast: Spell release sounds (when spell fires)
- Impact: Spell hit sounds (when spell hits target)

Power levels:
- Low: Weak spells, low level abilities
- Medium: Standard power spells
- High: Powerful high-level spells

Sound coverage (35+ sounds):
- 16 precast sounds (Fire/Frost/Holy/Nature/Shadow × Low/Med/High + Arcane)
- 5 cast sounds (one per school)
- 16 impact sounds (Fireball ×3, Blizzard ×6, Holy ×4, Arcane Missile ×3)

Technical details:
- Loads 35+ sound files from Sound\Spells directory
- Simple API: playPrecast(school, power), playCast(school), playImpact(school, power)
- Convenience methods: playFireball(), playFrostbolt(), playHeal(), etc.
- Random variation selection for impacts
- Volume at 0.75 with global scale control
- Ready for integration with spell casting system

Usage examples:
```cpp
// Full spell sequence
spellSoundManager->playPrecast(MagicSchool::FIRE, SpellPower::HIGH);
// ... cast time ...
spellSoundManager->playCast(MagicSchool::FIRE);
// ... projectile travel ...
spellSoundManager->playImpact(MagicSchool::FIRE, SpellPower::HIGH);

// Convenience methods
spellSoundManager->playFireball();
spellSoundManager->playHeal();
```

This adds essential magic feedback for spell casting gameplay!

CMakeLists.txt

@@ -108,6 +108,7 @@ set(WOWEE_SOURCES
     src/audio/ambient_sound_manager.cpp
     src/audio/ui_sound_manager.cpp
     src/audio/combat_sound_manager.cpp
+    src/audio/spell_sound_manager.cpp
 
     # Pipeline (asset loaders)
     src/pipeline/mpq_manager.cpp