feat: Batch Claiming for Multi-Schedule Beneficiaries

[BarryArinze]

🧩 Overview

This PR adds a batch_claim function that allows beneficiaries with multiple vesting schedules (e.g. Seed, Private, Advisory) to claim all currently unlocked tokens in a single transaction.

Previously, users needed to submit separate claims for each schedule, resulting in unnecessary gas costs and friction. This update consolidates claims into one efficient transaction.

⚙️ Key Features

• Added batch_claim() for addresses with multiple schedules
• Aggregates claimable balances across all linked schedules
• Executes a single token transfer
• Updates each schedule’s claimed amount atomically
• Skips inactive or fully claimed schedules
• Prevents duplicate claiming

🏗️ Implementation Details

• Fetch all schedules mapped to caller address
• Compute vested but unclaimed tokens per schedule
• Sum all available claimable amounts
• Persist claimed state before transfer
• Transfer total amount once to beneficiary

⛽ Gas & UX Benefits

• One transaction instead of many
• Lower cumulative gas spend
• Reduced wallet interaction friction
• Better experience for advisors and investors with multiple allocations

🔐 Security Considerations

• Checks-effects-interactions flow maintained
• Reverts when total claimable amount is zero
• Accurate per-schedule accounting preserved
• Compatible with existing vesting logic

🧪 Testing

Added coverage for:

• Beneficiary with multiple active schedules
• Mixed vested/unvested schedules
• Fully claimed schedules skipped
• Zero claimable balance revert
• Correct aggregate payout amount
• Claimed balances updated after batch execution

🚀 Impact

• Significant UX improvement for multi-tranche beneficiaries
• Lower operational claim costs
• Cleaner vesting claim workflow
• Improved contract efficiency

🔗 Related Issue

Closes #201

🏷️ Labels

ux, optimization, gas

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