Fix user-estate export production tenant

[mikaelbjorn]

Summary

Corrects the user-estate evidence export tenant from panorama-default to panorama.

Root cause

The user-estate export service defaulted DB_GATEWAY_TENANT_ID to panorama-default, and the production runtime configuration also explicitly selected that tenant. The actual PanoramaBlock user estate is stored under panorama.

Changes

• change the user-estate export fallback tenant to panorama
• correct backend/.env.example
• add a regression test proving all user-estate database requests use panorama when no explicit tenant override is configured

Verification

• regression reproduced before implementation: expected panorama, received panorama-default
• focused test suite: 4/4 passing
• git diff --check: PASS
• production runtime corrected to DB_GATEWAY_TENANT_ID=panorama
• production execution container healthy
• exact production export DB Gateway contract verified:
  • page 1: 1000 profiles
  • page 2: 118 profiles
  • total: 1118 profiles
  • tenant: panorama
  • functional data-path verification: PASS

The transaction-evidence tenant default is intentionally outside the scope of this change.