feat: implement whitelist and blacklist for events and users

[greatest0fallt1me]

Description:

Allow admin to maintain whitelists/blacklists (e.g., allowed/blocked users for betting, or allowed/blocked event creators) and enforce them in place_bet and create_event.

Requirements and Context:

• Must be secure, tested, and documented
• Should support user whitelist (only listed users can bet) or blacklist (listed users cannot bet)
• Should support event-level or global list
• Should allow admin to add/remove addresses
• Should enforce in contract logic and emit clear errors
• Must not break existing behavior when lists are empty/disabled

Suggested Execution:

1. Fork the repo and create a branch

   git checkout -b feature/whitelist-blacklist

2. Implement changes

   • Write contract: src/lib.rs (check list in place_bet/create_event)
   • Add list module: src/lists.rs (or storage helpers)
   • Update storage and events; add documentation and NatSpec-style comments

3. Test and commit

   • Run tests; cover whitelist-only, blacklist-only, add/remove
   • Include test output and security notes

Example Commit Message:

feat: implement whitelist and blacklist for events and users

Guidelines:

• Minimum 95 percent test coverage
• Clear documentation
• Timeframe: 72 hours