Add Operator Tools tab for claiming commission across all delegations

[koenmtb1]

• New /operator tab (only visible to wallets registered as providerAdmin or providerRewardsRecipient) that surfaces every split contract paying the operator, breaks the claimable amount into pending-distribute vs already-in-warehouse, and bundles claim → distribute → withdraw into the cart as one multicall.
• Reuses the same three-way breakdown (total / pending / warehouse) inside the existing delegator-side "Claimable Rewards" card so users can see exactly which stage their rewards are in.
• Indexer: /api/providers/:id now LEFT-JOINs atpPosition to expose the delegator beneficiary per stake, required to rebuild splitData for Split.distribute(). New field is additive and nullable.
• Removed the 256-entry hard cap in useMulticall3Execution — large operator carts now chunk into multiple multicalls (gas-aware) instead of falling back to one-by-one execution.