Add AI cost insights dashboard; rota-informed forecast method

AI Insights: a daily Claude-generated wage cost briefing covering
month-to-date pace vs budget, prior-month/prior-year comparison,
rota-vs-actual variance by department, a rota-informed forecast to
month-end, employee-level anomalies, and wage cost as a % of revenue.
Runs on a configurable daily schedule or on demand, gated by a manual
5-minute rate limit and a daily token budget. Uses the Anthropic key
configured centrally in Portal → Settings → Integrations.

Also includes the rota-vs-repeat-pattern forecast method (published/
draft rota tiers with same-weekday fallback) already built into the
Weekly/Monthly views, and adds a .gitignore for node_modules/dist.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/src/lib/forecasting-client.js

@@ -0,0 +1,13 @@
+import { getConfig } from '../db.js'
+
+export async function fcFetch(path) {
+  const apiKey  = await getConfig('forecasting_api_key')
+  const baseUrl = (await getConfig('forecasting_url')) || 'http://10.10.10.113:3080'
+  if (!apiKey) throw new Error('Forecasting API key not configured — add it in Settings')
+  const res = await fetch(`${baseUrl}/forecasting/api/public${path}`, {
+    headers: { 'X-API-Key': apiKey },
+    signal: AbortSignal.timeout(15000),
+  })
+  if (!res.ok) throw new Error(`Forecasting API ${res.status} — ${path}`)
+  return res.json()
+}