Feature/campaign contract

[LaGodxy]

🏗️ Core Features Implemented:

1. Storage Management:

   • CAMPAIGN_MAP: Map for storing campaign data
   • CAMPAIGN_COUNT: Counter for total campaigns

2. Data Structures:

   • Campaign tuple: (id, owner, goal, deadline, status, created_at)
   • CampaignStatus constants: Active (0), Completed (1), Cancelled (2), Expired (3)

3. Contract Functions:

   • ✅ register_campaign(env, owner, goal, deadline) -> u64
   • ✅ get_campaign(env, campaign_id) -> Campaign
   • ✅ update_campaign_status(env, campaign_id, status)
   • ✅ get_campaign_count(env) -> u64

4. Events:

   • ✅ CampaignRegistered: Emitted when new campaign is created
   • ✅ CampaignStatusUpdated: Emitted when campaign status changes

🔧 Technical Implementation:

• Soroban Compatible: Uses tuples instead of custom structs for WASM compatibility
• Proper Authentication: owner.require_auth() ensures only campaign owners can update status
• Efficient Storage: Map-based storage with proper instance storage
• Event System: Structured events for off-chain monitoring
• Error Handling: Proper panic messages for invalid operations

✅ Verification:

• WASM Compilation: Contract successfully compiles to wasm32-unknown-unknown target
• Type Safety: All functions properly typed with Soroban SDK types
• Storage Pattern: Follows established patterns from other contracts in project

📋 Acceptance Criteria Met:

• ✅ Contract compiles to WASM
• ✅ Campaign can be registered with unique ID
• ✅ Campaign data can be retrieved from storage
• ✅ Status updates work with proper authorization
• ✅ Events are emitted for key operations

closes #26