Add a JSONB column on the users table that stores an ordered list of
provider preferences for multi-provider redundancy. Each entry carries
{ providerType, priority, enabled }; credentials still live in the
dedicated encrypted columns so AES-256-GCM key rotation keeps working
unchanged. Null preserves the legacy single-provider resolution path.
Ships a defensive parser/serializer pair with a sensible default chain
(codex -> openai -> anthropic -> local -> admin-openai) so a malformed
JSON on disk falls back to the default rather than 500-ing insight
generation.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
