Fix ReclaimFunds hanging forever when the context is cancelled mid-sweep

[damilolaedwards]

Summary

• OnComplete is documented as always being called once transaction processing finishes, regardless of success or failure. The guard that returns early when the context is already cancelled skipped that contract entirely, returning before the callback was ever wired up.
• ReclaimFunds depends on that contract: it fires one goroutine per wallet to send a reclaim transaction and only calls wg.Done() from inside OnComplete, then waits on the group. Both a daemon shutdown and a spammer pause cancel the same context passed down to these sends, so any reclaim still being dispatched at that moment would never release its slot in the wait group, leaving the whole reclaim, and the spammer run it belongs to, stuck forever with no timeout to recover.
• The early-return path now calls OnComplete with the context error before returning, so every caller relying on it firing keeps working correctly once the context is cancelled.

Test plan

• Added a test driving the real transaction submission path with an already-cancelled context, asserting OnComplete still fires.
• Added a test mirroring ReclaimFunds's own wait group wiring end to end, confirming it no longer hangs.
• Both verified to fail against the previous behavior and pass with the fix, under -race.