fix: cap NATS JetStream streams to prevent OOM crash

WIRELESS_REGISTRATIONS stream had a 256MB MaxBytes cap in a 256MB
container — guaranteed to crash under load. ALERT_EVENTS and
OPERATION_EVENTS had no byte limit at all.

- Reduce WIRELESS_REGISTRATIONS MaxBytes from 256MB to 128MB
- Add 16MB MaxBytes cap to ALERT_EVENTS and OPERATION_EVENTS
- Bump NATS container memory limit from 256MB to 384MB
- Add restart: unless-stopped to NATS in base compose
- Bump version to 9.8.2

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/services/sse_manager.py

@@ -63,6 +63,7 @@ async def ensure_sse_streams() -> None:
                 name="ALERT_EVENTS",
                 subjects=["alert.fired.>", "alert.resolved.>"],
                 max_age=3600,  # 1 hour retention
+                max_bytes=16 * 1024 * 1024,  # 16MB cap
             )
         )
         logger.info("nats.stream.ensured", stream="ALERT_EVENTS")
@@ -72,6 +73,7 @@ async def ensure_sse_streams() -> None:
                 name="OPERATION_EVENTS",
                 subjects=["firmware.progress.>"],
                 max_age=3600,  # 1 hour retention
+                max_bytes=16 * 1024 * 1024,  # 16MB cap
             )
         )
         logger.info("nats.stream.ensured", stream="OPERATION_EVENTS")