feat(dkg): distribute dkg committee rewards from ubi

[0xHansLee]

Summary

• Distribute a configurable portion (DKGRewardPortion) of UBI rewards to active DKG committee members each block via DistributeRewardsToActiveCommittee when processing UBI withdrawal in evmstaking keeper
• Settle rewards for the previous committee during FinalizeDKGRound via settleRewardsForPreviousCommittee, storing any remainder in SettlementBalance in BeginBlocker of DKG module
• Sweep settlement balance in evmstaking's ProcessUbiWithdrawal via ClaimSettlementBalance to avoid circular module dependency
• Wire DKGKeeper into evmstaking through depinject (one-way: evmstaking → DKG)

Design

The DKG and evmstaking modules cannot depend on each other. To resolve this:

1. evmstaking → DKG (depinject): evmstaking calls DKGKeeper.DistributeRewardsToActiveCommittee() and DKGKeeper.ClaimSettlementBalance() during EndBlock
2. DKG → evmstaking (settlement pattern): During FinalizeDKGRound, the DKG module settles rewards for the previous committee using its own module balance and stores any remainder in SettlementBalance during BeginBlocker. evmstaking picks this up in the EndBlock cycle.

Changed files

Area	Files	Description
DKG rewards	dkg_rewards.go	Core reward distribution and settlement logic
DKG keeper	keeper.go, depinject.go	Add BankKeeper, DistributionKeeper deps; SettlementBalance collection
DKG finalization	dkg_finalization.go	Call settleRewardsForPreviousCommittee on round finalize
DKG params	params.proto, params.go	Add DKGRewardPortion parameter
DKG events	event.proto, dkg_events.go	Add EventDKGRewardsDistributed
evmstaking UBI	ubi.go	Integrate DKG settlement sweep and committee reward deduction
evmstaking wiring	keeper.go, depinject.go, expected_keepers.go	Add DKGKeeper interface and depinject
Tests	dkg_rewards_internal_test.go, ubi_test.go, abci_test.go, etc.	26 new DKG reward tests, updated evmstaking tests

issue: none