ops(registry): convert stale-type backfill from script to migration

[EmmaLouise2018]

Summary

• Replaces server/scripts/backfill-member-agent-types.ts (ops(registry): backfill stale member_profiles.agents types + crawler reclassify-on-disagreement #3541) with migration 463_backfill_member_agent_types_from_snapshot.sql.
• The TS script lived under server/scripts/ — outside server/src/ — so tsc skipped it and it never shipped to the production container. Running it via fly ssh console failed with ERR_MODULE_NOT_FOUND.
• The migration applies the same resolveAgentTypes() logic in SQL, runs automatically on the next deploy in every env, and writes its audit trail to type_reclassification_log with run_id='migration-463' in one transaction with the data update.

What it does

For every row in member_profiles.agents whose URL has a row in agent_capabilities_snapshot:

• snapshot inferred_type is valid → set agent's type to it
• snapshot exists but inferred_type is null/invalid → set 'unknown' (anti type-smuggling, matches resolveAgentTypes)
• no snapshot → leave the agent untouched

Audit query post-deploy:

SELECT * FROM type_reclassification_log WHERE run_id = 'migration-463';

Test plan

• npm run typecheck clean
• npm run build clean
• npm run test:migrations clean (filename pattern, no duplicate version, no gap)
• Pre-commit hooks (test:unit + test:test-dynamic-imports + test:callapi-state-change + typecheck) passed
• On staging: confirm migration applies cleanly, verify run_id='migration-463' rows match the JSONB diff
• On prod: same verification after deploy

Refs #3538, #3541, #3550.