BOLT-1194: /callback observability — log underlying error + correlation id

Improve apps/auth /callback route error observability. Catch-all on line 174 silently swallows errors when Sentry transport fails. Add structured warn log with error.name/message/code + correlation_id, return correlation_id in JSON response. Apply to all three jsonError paths (113, 104, 174). Discovered during [email protected] incident 2026-06-05.