flowfi

[Gogo-Eng]

Closes #799
Closes #788
Closes #805

[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.)

[ogazboiz]

the split pause/resume errors (StreamAlreadyPaused / StreamNotPaused) + tests are a good improvement. one real fix: cargo fmt --check fails on a stray blank line at contracts/stream_contract/src/errors.rs:33, run cargo fmt from contracts/ and commit. the backend/npm red is stale (unrelated files), so after cargo fmt, rebase on main and it'll go green.