fix: skip unparseable and foreign sync ids in traffic triggers (Scala)

[sadiq1971]

Two SV traffic triggers treat a MemberTraffic contract they cannot act on as a fault. Traffic can be purchased for any registered synchronizer, so an SV's sequencer legitimately observes contracts naming synchronizers it does not serve. Scala side only, no Daml or config changes.

What this does

• SynchronizerId.tryFromString -> fromString + fold in both triggers. The throwing variant fails the trigger and leaves it retrying the same contract; the Either form skips it with a TaskSuccess, matching how memberId is already handled directly above in both files.
• ReconcileSequencerLimitWithMemberTrafficTrigger no longer raises Status.INTERNAL when the contract names a different synchronizer. Those grants are applied by that synchronizer's own operator on its own sequencer, so this node skips them rather than failing.
• MergeMemberTrafficContractsTrigger parses ahead of the for comprehension, dropping a getDsoRules() round trip on ids that are skipped anyway.

How it's verified

apps-sv/compile, scalafmtCheck, headerCheck and scalafix --check all pass locally.

No new tests: apps/sv holds 79 triggers and no trigger unit tests, so this follows the existing pattern.

Both skip paths land in the Appendix B acceptance e2e (register, buy, then reconcile across two synchronizers), which needs the two-synchronizer topology the foreign path requires anyway. Naming it here so the debt is tracked rather than implicit.

One forward-looking note for whoever writes that test: the case that feeds an unparseable synchronizer id will trip the CI log gate on the logger.warn added in 4d4b9af, and needs an ignore-pattern entry alongside the test.

Tracked in

Implements E2-3 (ChainSafe/canton-extending-mainnet#33).

[timwu20]

One pre-merge mechanical: the branch predates the #8/#12 squashes, so it lacks the Flyway ignore-pattern fix that rode in with #12 — the two red checks are the Aug-13 known flakes (simtime clog gate with sbt green underneath), but any fresh run on this tree will fail ~7 jobs on the Postgres-18.6 pattern. Suggest rebasing onto current feat/dedicated-sync (5186e84) and letting [ci] rerun; expect green, then this is merge-ready. (#15 stacks on this branch, so it rebases in the same pass.)