fix: correct timeslot search and allocation in RequestTranslator

[youf3]

Summary

• Fix find_common_timeslots computing a slot_mask from the raw sequence length, which could
  be millions of slots for idle-wait agents (e.g. a node waiting for the full experiment). This
  caused bitarray.find() to return -1 because the search pattern was longer than the search
  space; the fix caps the mask to MAX_TIMESLOTS.
• Add an explicit exception when find() returns -1 so the failure surfaces with a clear
  message instead of silently producing a wrong slot assignment.
• Fix slot-allocation loop: extract assigned = timeslot_mask[:timeslot] before advancing the
  mask pointer, and skip empty assignments. The previous order could produce off-by-one
  allocations.
• Increase submit() timeout from 5 s → 30 s to give agents enough time to respond under load.
• Raise MAX_TIMESLOTS from 500 → 1000 to accommodate longer experiments.
• Set max_packet_size 268435455 in the regression-test Mosquitto config to allow large DQC
  request payloads.