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/server_mappers.py

@@ -0,0 +1,37 @@
+"""Server response mappers.
+
+Convert domain models (from server_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.server import ServerSettings, ServerSettingsResponse, ServerSettingsUpdate
+from app.models.server_domain import DomainServerSettings, DomainServerSettingsResult
+from app.utils.pagination import create_pagination_metadata
+
+
+def map_domain_server_settings_to_response(
+    domain_settings: DomainServerSettings,
+) -> ServerSettings:
+    """Convert domain server settings to response model."""
+    return ServerSettings(
+        log_level=domain_settings.log_level,
+        log_target=domain_settings.log_target,
+        syslog_socket=domain_settings.syslog_socket,
+        db_path=domain_settings.db_path,
+        db_purge_age=domain_settings.db_purge_age,
+        db_max_matches=domain_settings.db_max_matches,
+    )
+
+
+def map_domain_server_settings_result_to_response(
+    domain_result: DomainServerSettingsResult,
+) -> ServerSettingsResponse:
+    """Convert domain server settings result to response model."""
+    return ServerSettingsResponse(
+        settings=map_domain_server_settings_to_response(domain_result.settings),
+        warnings=domain_result.warnings,
+    )