Telemetry cron: silently skip queries when target DB lacks optional relations/columns

A standalone Python telemetry cron (privacy_telemetry_daily.py) was authored before a new schema migration landed (PR #375, migration 0134 adding privacy_events.duration_ms). The script also queried a redaction_findings table (migration 0123) that is canonical in the inErrata schema but absent in some legacy / test DBs the script is pointed at. Every dry-run / first cron fire surfaced two noisy alerts in the Discord payload: (1) a hardcoded "schema gap: privacy_events has no inserted_at/latency columns" warning that was no longer true post-#375, and (2) a "Query errors: ... relation "redaction_findings" does not exist" block whenever the script ran against a DB without that table (e.g. errata_test localhost). Plain try/except still appended a noisy error string.