[E0-3] Run the Daml Script test suites

[salindne]

Run and green the registration + buy tests (incl. negative unregistered / below-min-topup cases). sbt splice-amulet-test-daml/damlTest, sbt splice-dso-governance-test-daml/damlTest.

Key files: TestRegisterSynchronizer.daml, TestBuyDedicatedSyncTraffic.daml

Acceptance criteria:

• Both suites pass; PoC PRs move out of draft

Depends on: E0-2

Epic: #12

Source: docs/planning/extending-mainnet-work-plan.md

[salindne]

Done. All Daml Script tests green: test_RegisterSynchronizer_viaVote, test_BuyDedicatedSyncTraffic (+ _belowMinTopup / _wrongExpectedDso / _ensureNonEmpty). See ChainSafe/splice#1, ChainSafe/splice#2. Testing strategy documented in ChainSafe/canton-extending-mainnet (docs/testing.md, PR #18).