fix(streaming): reject backdated start_time, add pagination overflow regression test

[davidsoniaudin2-oss]

Summary

Solves the four issues assigned to this account on the streaming contract and the affected frontend surfaces. Two required real changes (both in contracts/streaming), and two turned out to already be fixed on main — details below.

Fixes #221, #222

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#221 — create_stream / create_streams_batch now reject backdated start_time ✅ fixed

Problem: Neither entrypoint validated start_time against the current ledger time, so a sender could backdate start_time/cliff_time and have a large chunk of the deposit unlocked (and withdrawable) the moment the stream was created, bypassing the vesting UX.

Change (contracts/streaming/src/lib.rs):

• New typed error variant StreamError::PastStartTime = 21.
• create_stream: rejects start_time < env.ledger().timestamp() (returning PastStartTime) before any funds move.
• create_streams_batch: same check per-input in phase-1 validation, so a single backdated input rejects the entire batch atomically with no partial state and no funds moved.
• Backdated cliff_time (cliff before start) was already rejected as InvalidCliff; it now has explicit test coverage.

Tests added (test.rs, test_batch.rs):

• test_create_stream_rejects_past_start_time — asserts PastStartTime and that no funds moved.
• test_create_stream_rejects_backdated_cliff — asserts InvalidCliff.
• test_batch_rejects_past_start_time — asserts PastStartTime plus atomicity (no stream created, contract balance unchanged).

#222 — pagination no longer aborts on offset + limit overflow ✅ fixed (fix on main) + regression test added

Problem: get_sent_streams / get_received_streams / get_archived_* computed offset + limit as a raw u32; with overflow-checks = true in Cargo.toml a large combination aborted the read call.

Status: The clamping fix already landed on main — the shared paginate helper (introduced in #475) uses offset.checked_add(limit) and clamps both bounds to the vector length, returning an empty page for out-of-range offsets instead of aborting. What was missing is exactly what the issue asked for: a regression test.

Test added (test.rs):

• test_pagination_clamps_large_offset_limit — creates 5 streams and asserts:
  • offset=2, limit=u32::MAX (overflows u32) → clamps to the tail (3 entries) instead of aborting;
  • offset=u32::MAX, limit=u32::MAX → empty page, no abort;
  • offset=0, limit=u32::MAX → full page still works.

#224 — use-batch-create unmount cleanup ✅ already fixed on main

hooks/use-batch-create.ts already contains the unmount cleanup:

useEffect(() => {
  return () => {
    abortRef.current = true
  }
}, [])

Landed in d535901 ("fix(hooks): add unmount cleanup to useBatchCreate", merged via PR #335). The in-flight batch loop aborts as soon as the component unmounts, so no wallet-signature prompts fire after navigating away. No code change needed — the issue can be closed.

#456 — landing page SSR/hydration mismatch ✅ already fixed on main

components/landing/live-stream-preview.tsx no longer computes a module-level NOW. The demo stream is seeded inside the useState initializer:

const [demoStream] = useState(() => buildDemoStream(Math.floor(Date.now() / 1000)))

so server and client render the same markup on first paint (the initializer-based approach the issue's suggested fix calls for). Landed in 59ba171 ("…fix SSR hydration mismatch…"). No code change needed — the issue can be closed.

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Verification

⚠️ Note: I could not run cargo test locally — this environment has no Rust toolchain (and the user opted to skip installing one). The contract changes were reviewed manually against the existing code and test conventions:

• The new checks reuse the existing env.ledger().timestamp() pattern already used by top_up/withdraw/cancel.
• All existing tests create streams with start_time >= the current ledger timestamp (they call set_time(now) before create_stream with start_time: now), so the new check should not break any of them.
• New tests follow the exact assert_eq!(result, Err(Ok(StreamError::…))) pattern used throughout the suite.

Please let CI (cargo test in contracts/streaming) confirm. The frontend issues required no changes, so no frontend verification was needed.
closes #456
closes #222
closes #224
closes #221

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