Multisig Operations Tests

[stepanLav]

Files to create:
tests/integrations/tests/multisig-create.integration.test.ts
tests/integrations/tests/multisig-approve.integration.test.ts
tests/integrations/tests/multisig-execute.integration.test.ts
tests/integrations/fixtures/multisig/operations.ts

Coverage:

• Multisig account creation
• Transaction approval workflow
• Threshold logic (2-of-3, 3-of-5, etc.)
• Final approval and execution
• Cancellation flow