Add credit checking and deduction to my AI tool:

Before any AI API call:
1. Check user's credits_remaining
2. If credits_remaining > 0: proceed with AI request
3. If credits_remaining = 0: show upgrade message, block request

After successful AI response:
1. Deduct 1 from credits_remaining  
2. Add 1 to credits_used_this_month
3. Update user interface with new credit count

Error handling:
- If AI API call fails, don't deduct credits
- If user has 0 credits, show clear upgrade path
- If database update fails, log error but don't break user experience

UI requirements:
- Show credits remaining prominently in interface
- Clear upgrade button when approaching limits
- What they get when they upgrade

Please implement this credit checking and deduction system.