feat: reassemble raw inbound PDU SMS

[Justinabox]

Summary

• add a bounded raw SMS-DELIVER PDU ingestion path with multipart reassembly
• persist and publish only completed messages; preserve valid single-part deliveries
• fail closed for malformed, oversized, invalid-timestamp, and malformed UCS-2 PDUs
• use bounded opaque replay/retry identities to prevent duplicate delivery while allowing retries after failed persistence

Verification

• ........................................................................ [ 6%]
  ........................................................................ [ 12%]
  ........................................................................ [ 19%]
  ........................................................................ [ 25%]
  ........................................................................ [ 31%]
  ........................................................................ [ 38%]
  ........................................................................ [ 44%]
  ........................................................................ [ 51%]
  ........................................................................ [ 57%]
  ........................................................................ [ 63%]
  ........................................................................ [ 70%]
  ........................................................................ [ 76%]
  ........................................................................ [ 82%]
  ........................................................................ [ 89%]
  ........................................................................ [ 95%]
  ................................................ [100%]
  1128 passed in 7.64s (1128 passed)

Scope and risks

• Raw PDU ingestion foundation only; text-mode/CMTI multipart integration remains out of scope.
• No real hardware used.