Adds a new native `ipaws` adapter for FEMA IPAWS-OPEN EAS civil alerts.
- Two-stage CAP fetch via base_url (direct FEMA or Conduit proxy): Atom
index -> per-entry CAP 1.2 documents.
- Non-weather civil alerts only (evacuation, Civil Emergency Message,
AMBER, 911 outage, law-enforcement, HazMat); NWS/NOAA CAP dropped so
weather is never double-broadcast.
- Idaho + neighbour statefips scope gate applied before stage-2 fetch.
- Own `ipaws_alerts` dedup table (migration v29); reuses the NWS CAP
severity + formatter pattern.
- Ships enabled=False (no transmit until explicitly enabled).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
