D3: flush settled 1m oracle bars + trigger incremental coarse rollup

Per-minute cron flush: drains settled minute bars from the accumulator into price_bars, then re-derives the affected 15m/1h/4h/1d windows.

pg_cron schedule: every minute. Dead-man 2x = 120s. FOUNDER-GATED to have effect: PYTH_LIVE_ROLLUP_ENABLED must be True; until then the accumulator stays empty and this flush is a no-op.