feat: Add comprehensive event system to Jackpot Wall contract

[syed-ghufran-hassan]

• Add post-created event for every new post with metadata
• Add jackpot-won event with jackpot ID, amount, and pot details
• Add pot-updated event for tracking pot balance changes
• Add emergency-withdrawal event for admin actions
• Add new-post event for non-jackpot posts

feat: Add protocol statistics and tracking

• Add total-stx-collected counter
• Add total-stx-paid counter
• Add last-jackpot-height and last-jackpot-amount tracking
• Add jackpot-count for total jackpots awarded
• Add get-protocol-stats read-only function

feat: Add user statistics tracking

• Add user-stats-map for tracking user activity
• Track posts made, jackpots won, total earned, total spent
• Add get-user-stats read-only function

feat: Add jackpot history tracking

• Add jackpot-history map for complete jackpot records
• Track post ID, winner, amount, block height, total posts at time
• Add get-jackpot-history read-only function

feat: Enhance post data structure

• Add timestamp to posts
• Add is-jackpot flag
• Add jackpot-amount field for winning posts

fix: Resolve naming conflict in user-stats map

• Rename user-stats map to user-stats-map to avoid conflict with let binding variable
• Update all references to user-stats-map accordingly
• Fix variable naming in let bindings for clarity