feat: add Loki log query support to lab-monitoring

Add 3 opt-in Loki tools (query_logs, list_labels, list_label_values)
that are registered when LOKI_URL is configured. Includes Loki HTTP
client, CLI commands (logs, labels), NixOS module option, formatting,
and tests.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/mcp/server.go

@@ -83,7 +83,7 @@ This ensures package information matches the nixpkgs version the project actuall
 func DefaultMonitoringConfig() ServerConfig {
 	return ServerConfig{
 		Name:    "lab-monitoring",
-		Version: "0.1.0",
+		Version: "0.2.0",
 		Mode:    ModeCustom,
 		Instructions: `Lab Monitoring MCP Server - Query Prometheus metrics and Alertmanager alerts.
 
@@ -92,8 +92,9 @@ Tools for querying your monitoring stack:
 - List and inspect alerts from Alertmanager
 - View scrape target health status
 - Manage alert silences
+- Query logs via LogQL (when Loki is configured)
 
-All queries are executed against live Prometheus and Alertmanager HTTP APIs.`,
+All queries are executed against live Prometheus, Alertmanager, and Loki HTTP APIs.`,
 	}
 }