Spell and effect fixes

1. Skill adjustment: Adjustments were made to optimize certain skills.

2. EXP item fix: Fixed an issue where the multiplier for some EXP items was incorrect.

3. Effect item fix: Resolved the issue that prevented some effect items from being used properly.

4. Hell Garden Towers seeds > 6 fix: Adjusted seeds for Hell Garden Towers above level 6.

5. Event item stacking adjustment: Increased the stacking limit of event items from 50 to 255.

6. Alt character limit: Implemented a limit on the use of alternate characters (alts) in Hell Garden Towers and Gilles de Rais Lair.

7. Sound added to skills: Added sound effects to skills 251, 261, and 271.