Fix HIGH priority issues: unbounded queries, rate limiting, health checks

Issue #3 - Unbounded Query Results (OOM):
- get_all_archived_history() now uses keyset pagination with bounded max_rows (50k default)
- Added 'id' field to records from get_archived_history() and get_archived_history_keyset()
- Protocol signature updated with page_size, max_rows, last_ban_id params

Issue #7 - Docker Health Check Fails:
- Added curl to Dockerfile.backend runtime image
- HEALTHCHECK now uses 'curl -f http://localhost:8000/api/health'
- compose.prod.yml: increased start_period to 40s, timeout to 10s
- Frontend healthcheck proxies to backend /api/health

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/mappers/health_mappers.py

@@ -0,0 +1,23 @@
+"""Health response mappers.
+
+Convert domain models (from health_service) to response models (for HTTP API).
+
+This is the mapping layer at the router boundary, ensuring the service layer
+remains independent of HTTP response shapes.
+"""
+
+from __future__ import annotations
+
+from app.models.health_domain import DomainServerStatus
+from app.models.server import ServerStatus
+
+
+def map_domain_server_status_to_response(domain: DomainServerStatus) -> ServerStatus:
+    """Convert domain server status to response model."""
+    return ServerStatus(
+        online=domain.online,
+        version=domain.version,
+        active_jails=domain.active_jails,
+        total_bans=domain.total_bans,
+        total_failures=domain.total_failures,
+    )