feat(digest): add weekly capacity digest email cron

Sends a Monday digest to all ADMIN + MANAGER users with:
- Team utilization % for the next 4 weeks
- Overbooked resource count
- Open demand count
- Upcoming vacation count
- Top 5 most utilized resources

Route: GET /api/cron/weekly-digest (secured by CRON_SECRET).
HTML template and plain-text fallback included.

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

apps/web/src/app/api/cron/weekly-digest/route.ts

@@ -0,0 +1,40 @@
+import { NextResponse } from "next/server";
+import { prisma } from "@capakraken/db";
+import { sendWeeklyDigest } from "@capakraken/api";
+import { logger } from "@capakraken/api/lib/logger";
+import { verifyCronSecret } from "~/lib/cron-auth.js";
+
+export const dynamic = "force-dynamic";
+export const runtime = "nodejs";
+
+/**
+ * GET /api/cron/weekly-digest
+ *
+ * Sends a weekly capacity digest email to all ADMIN and MANAGER users.
+ * Contains team utilization, overbooking count, open demand count, and
+ * upcoming vacations for the next 4 weeks.
+ *
+ * Secure with CRON_SECRET: requests must include `Authorization: Bearer <secret>`.
+ * Schedule: run every Monday morning (e.g. `0 7 * * 1` in cron syntax).
+ */
+export async function GET(request: Request) {
+  const deny = verifyCronSecret(request);
+  if (deny) return deny;
+
+  try {
+    // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    const result = await sendWeeklyDigest(prisma as any);
+
+    return NextResponse.json({
+      ok: true,
+      ...result,
+      sentAt: new Date().toISOString(),
+    });
+  } catch (error) {
+    logger.error({ error, route: "/api/cron/weekly-digest" }, "Weekly digest cron failed");
+    return NextResponse.json(
+      { ok: false, error: "Internal error" },
+      { status: 500 },
+    );
+  }
+}