feat(tm2): add transfer event for bank ops

[MikaelVallenet]

Summary

The bank module looks was ported with all event emission commented out.
Now that Gno has typed ABCI events (#4630), this PR wires them up.

Three event types are introduced:

• TransferEvent — 1:1 transfers, carries from, to, amount
• CoinSpentEvent — coins leaving an account (per-input in multi-send)
• CoinReceivedEvent — coins entering an account (per-output in multi-send)

Using separate types for multi-send avoids zero-address sentinels that would confuse indexers. No event is emitted when the amount is zero.

partial fix #5344

Known limitations

• Gas fee transfers emit events but are not visible in tx results (ante handler runs before runMsgs() creates a
  fresh EventLogger).
• Realm-level minting/burning bypasses sendCoins(), dedicated MintEvent/BurnEvent should be introduced
  separately.

[Gno2D2]

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Codecov Report

❌ Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
tm2/pkg/sdk/bank/events.go	0.00%	3 Missing ⚠️

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