Fix: SQLite integer 0 rendering as text, NaN avg response display

- maintenance_mode and hasActiveIncident are SQLite integers (0/1), not JS booleans.
  {0 && <span>} evaluates to {0} which React renders as the text "0" in the DOM.
  Fixed with !! coercion on both conditions in renderResourceRow.

- avgResponseTime can be NaN for resources with no checks (e.g. icmp with no data).
  Added || 0 guard in the aggregate average and —/ms conditional in the row display.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/build/index.html

@@ -1 +1 @@
-<!doctype html><html lang="en"><head><meta charset="utf-8"/><link rel="icon" type="image/png" href="/app-icon.png"/><meta name="viewport" content="width=device-width,initial-scale=1"/><meta name="theme-color" content="#000000"/><meta name="description" content="SkyWatch - Infrastructure monitoring and alerting system"/><link rel="apple-touch-icon" href="/app-icon.png"/><link rel="manifest" href="/manifest.json"/><title>SkyWatch</title><script defer="defer" src="/static/js/main.85e69234.js"></script><link href="/static/css/main.67d2dbc4.css" rel="stylesheet"></head><body><noscript>You need to enable JavaScript to run this app.</noscript><div id="root"></div></body></html>
+<!doctype html><html lang="en"><head><meta charset="utf-8"/><link rel="icon" type="image/png" href="/app-icon.png"/><meta name="viewport" content="width=device-width,initial-scale=1"/><meta name="theme-color" content="#000000"/><meta name="description" content="SkyWatch - Infrastructure monitoring and alerting system"/><link rel="apple-touch-icon" href="/app-icon.png"/><link rel="manifest" href="/manifest.json"/><title>SkyWatch</title><script defer="defer" src="/static/js/main.1e7808e0.js"></script><link href="/static/css/main.67d2dbc4.css" rel="stylesheet"></head><body><noscript>You need to enable JavaScript to run this app.</noscript><div id="root"></div></body></html>