BOLT-1089: Fix VEN registration review comments

Artem asked in Slack thread 1780036222.881059 / message 1780222416.000059 to fix relevant comments from merged PR #11249 (BOLT-1051). Scope: adapters/program VEN registration repository. Fix 1: lazy-load prisma/repository in venRegistrationRepository.integration.test.ts only when RUN_INTEGRATION=true to preserve DB-free default test discovery. Fix 2: add lastPollAt:null to upsert update branch so re-registration resets stale poll liveness state. Update unit/integration assertions. Branch: artem-agent/bolt-1089-ven-registration-review-fixes. Open PR linked to BOLT-1089, monitor CI.