docs: add guidance for large deployments (30+ nodes) in rate limit config

Update config.example.yaml with:
- Recommendations for very large deployments (30+ nodes)
- Formula for calculating optimal rate limits based on node count
- Example calculation: 30 nodes with 10s polling = 300ms interval
- Security note about minimum safe intervals

This helps admins properly configure the proxy for enterprise
deployments with dozens of nodes.

cmd/pulse-sensor-proxy/config.example.yaml

@@ -29,11 +29,19 @@ metrics_address: "127.0.0.1:9127"
 # Adjust these values based on your deployment size:
 #   - Small (1-3 nodes): Use defaults (1000ms, burst 5)
 #   - Medium (4-10 nodes): 500ms, burst 10
-#   - Large (10+ nodes): 250ms, burst 20
+#   - Large (10-20 nodes): 250ms, burst 20
+#   - Very Large (30+ nodes): 100ms, burst 30-50
+#
+# Formula: To poll all nodes in one cycle, set burst >= node_count
+# For optimal performance: per_peer_interval_ms = (polling_interval_ms / node_count)
+# Example: 10 second polling with 30 nodes = 10000ms / 30 ≈ 300ms interval
 rate_limit:
-  per_peer_interval_ms: 1000  # Minimum milliseconds between requests per peer (1000ms = 1 qps)
+  per_peer_interval_ms: 1000  # Minimum milliseconds between requests per peer (1000ms = 1 qps = 60 requests/min)
   per_peer_burst: 5            # Number of requests allowed in a burst (supports up to 5 simultaneous requests)
 
 # Default values if not specified:
 #   per_peer_interval_ms: 1000 (1 second = 1 qps = 60 requests/min)
 #   per_peer_burst: 5
+#
+# Security note: Lower intervals increase throughput but also increase exposure
+# to potential abuse. For production, keep interval >= 100ms unless necessary.