fix: update rewards before direct claim

[sirakinb]

Fixes #2.

StakingV01.claimRewards paid only the stored rewardBalance. If a staker called claimRewards() before any unstake or owner reward update, accrued rewards were not first materialized into the stake info, so the claim could emit/pay 0 even though calculateRewardsIncrement() was positive.

This updates rewards before claiming in the base V1 implementation, matching the later V2 behavior and the expectation that a direct claim pays currently accrued rewards.

Also adds a regression test against the V1 staking fixture that:

• creates a stake
• advances time so rewards accrue
• verifies rewardBalance is still 0 before claim
• calls claimRewards() without unstaking first
• asserts a positive reward payout and a zero remaining reward balance

Verification performed locally:

• git diff --check
• python3 -m py_compile tests/test_staking_unstake_claim_rewards.py
• npx --yes solhint@3.6.2 contracts/staking/StakingV01.sol (0 errors; existing custom-error warnings only)

I could not run brownie test locally because Brownie is not installed on this machine, pip install eth-brownie is blocked by its pinned PyYAML==5.4.1 build on the local macOS/Python setup, and Docker is installed but the daemon is not running for the repository devcontainer.

[openzeppelin-code]

fix: update rewards before direct claim

Generated at commit: 28b48ceca81ebc3815cdcd07e8fbc0214c323ee2

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	0 1 0 7 22 30
Dependencies	Critical High Medium Low Note Total	0 0 0 1 8 9

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