fix: enforce max 100 active tournament escrows per player

[Davichi-1]

Overview

This PR adds a maximum cap on active tournament escrows per player to prevent storage bloat attacks. A malicious user could otherwise spam create_tournament_escrow to bloat contract storage and increase fees for everyone.

Related Issue

Closes #864

Changes

📈 Active Escrow Cap Enforcement

• [ADD] PLAYER_ACTIVE_ESCROWS storage key – a Map<Address, u32> tracking per-player active escrow count
• [ADD] MAX_ACTIVE_ESCROWS = 100 constant – maximum allowed active escrows per unique user address
• [ADD] player: Address field to TournamentEscrow struct to associate each escrow with its creator
• [ADD] MaxActiveEscrowsExceeded = 39 error variant
• [MODIFY] create_tournament_escrow – checks the per-player cap before creating, increments count on success
• [MODIFY] release_tournament_escrow – decrements the player's count upon release

Verification Results

cargo build -p game_contract
✅ Compiled successfully

cargo test -p game_contract
✅ 65/65 tests passed

Acceptance Criteria

Criterion	Status
Enforce a maximum cap (e.g., 100) on active escrows per unique user address	✅ Implemented with MAX_ACTIVE_ESCROWS = 100
Prevent storage bloat from create_tournament_escrow spam	✅ Per-player counter checked before each escrow creation
Active count decremented when escrow is released	✅ Count updated in release_tournament_escrow

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[chinweobtagaz]

@Davichi-1 conflicts

[chinweobtagaz]

@Davichi-1 please resolve conflicts