Gate stake, unstake, and set_boost behind pool pause guard

[Jennylila]

Overview

This PR fixes an inconsistency in the farming-pool emergency pause behavior. Previously, pause only blocked lock_assets and unlock_assets, while the boost/stake system (stake, unstake, set_boost) remained callable. This change enforces a unified pause invariant so paused pools cannot accept new stakes or boost changes.

Related Issue

Closes #28

Changes

🛡️ Pause Guard Enforcement

• [MODIFY] soroban/contracts/farming-pool/src/lib.rs
• Added pool_is_paused guard to stake
• Added pool_is_paused guard to unstake
• Added pool_is_paused guard to set_boost
• Left set_global_multiplier, pause, and unpause ungated so admins can act during emergencies
• Updated pause documentation to list all blocked functions

🧪 Tests

• [MODIFY] soroban/contracts/farming-pool/src/test.rs

• Added test_pause_blocks_stake and test_unpause_restores_stake

• Added test_pause_blocks_unstake and test_unpause_restores_unstake

• Added test_pause_blocks_set_boost and test_unpause_restores_set_boost

• Added test_set_global_multiplier_callable_while_paused to confirm admin ops still work while paused

• [ADD] soroban/contracts/farming-pool/test_snapshots/test/*.json

• Added test snapshots for the new pause-guard coverage

Verification Results

Acceptance Criteria	Status
stake blocked when pool is paused	✅
unstake blocked when pool is paused	✅
set_boost blocked when pool is paused	✅
set_global_multiplier remains callable while paused	✅
Test: paused → call → expect rejection (stake/unstake/set_boost)	✅
Test: unpause → call → expect success (stake/unstake/set_boost)	✅

cargo test -p farming-pool ✅ passed (57/57)

Test plan

• Run cargo test -p farming-pool and confirm all tests pass
• Confirm stake, unstake, and set_boost revert while paused
• Confirm those functions succeed again after unpause
• Confirm set_global_multiplier still works while paused