Get tipping pool balance day-over-day

Get daily pool balance (cumulative deposits - cumulative tips) for time-series charts (public, no auth).

• Returns the estimated pool balance at the end of each day.
• Computed as: cumulative deposits - cumulative tips up to that day.
• Also includes daily_deposits and daily_tips for each day.
• Useful for charts showing how the available tipping pool changes over time.
• Data points are ordered by date ascending (oldest first).
• window examples:
  • 24h: pool balance for the last 24 hours (1 day)
  • 7d: pool balance for the last 7 days
  • 30d: pool balance for the last 30 days
  • all: all-time data

Note: This is a derived metric computed from fund_events and tip_events. The current pool balance (/pool/total) may differ slightly due to timing.