test(stream): cover COMPLETED status and StreamEvent unique dedup

[Caneryy]

Closes #839

Summary

• [Testing] No test asserts @@unique([transactionHash,eventType]) dedup, and repository COMPLETED branch is untested

Test plan

• Relevant tests pass locally
• Manual verification on affected UI or API paths

[Caneryy]

@ogazboiz revier and merge please

[ogazboiz]

heads up: main's ci was broken (the Backend CI and Backend Docker Image CI jobs) until the fixes in #969 and #974 just landed, so the red backend/docker checks on this pr are almost certainly stale, they ran against the broken main. please rebase to re-test against the now-green main: git fetch origin && git rebase origin/main && git push --force-with-lease. once it's green i'll review and merge. (if a non-backend check like Frontend CI is still red after the rebase, that part is a real issue worth a look, since frontend ci was passing on main.)

[Caneryy]

all checks passed. review please. @ogazboiz