Updated `MASTER_ROADMAP_2026_Q1.md` and session logs to reflect completion of the Ping Service tracer bullet. Verified the end-to-end stack, including frontend, backend, and Gateway integration. Fixed query parameter mismatch in `PingApiKoinClient.syncPings()` (`lastSyncTimestamp` → `since`) for proper Delta-Sync functionality. Marked related roadmap tasks as completed.
Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>