Event stream compression and trimmed payloads

We enabled producer compression and trimmed the on-the-wire event payload across the Data pipeline.

1. All event-stream producers across the Data pipeline now use compression.
2. The events schema was pruned of fields that downstream consumers never read, reducing per-event size.
3. An optimized event format is now used for analytical consumers; the legacy unbounded payload is no longer published.
4. Result: lower internal storage usage and faster replay performance for backfills and recovery scenarios.