feat(plant-hours): GET /api/plant-hours/template route

Emits the canonical xlsx with a sample row derived from the first
vehicle in PocketBase. Falls back to a hardcoded sample if the
vehicles collection is empty.

src/app/api/plant-hours/template/route.ts

@@ -0,0 +1,57 @@
+import { NextResponse } from "next/server";
+import { pbAdmin } from "@/lib/pb";
+import { buildPlantHoursTemplateWorkbook } from "@/lib/plant-hours-template";
+
+/**
+ * GET /api/plant-hours/template
+ *
+ * Emits the canonical Plant_Hours_Template_2.xlsx workbook. The
+ * sample row's vehicle QR / description / cost-per-hour are pulled
+ * from the first vehicle in PocketBase (plant or fuel — doesn't
+ * matter, the template just needs plausible real data).
+ */
+export async function GET() {
+  const start = Date.now();
+  try {
+    const pb = await pbAdmin();
+    const first = await pb
+      .collection("vehicles")
+      .getList(1, 1, { sort: "description" })
+      .then((r) => r.items[0])
+      .catch(() => null);
+
+    const sample = first
+      ? {
+          qr_code_id: first.qr_code_id || "QR-A",
+          description: first.description || "Generator X",
+          cost_per_hour: first.cost_per_hour || 185,
+        }
+      : { qr_code_id: "QR-A", description: "Generator X", cost_per_hour: 185 };
+
+    // SheetJS returns a Uint8Array whose underlying buffer TS can't
+    // narrow to ArrayBuffer (the lib.dom Uint8Array<ArrayBuffer>
+    // generic is stricter than what XLSX.write emits). The xlsx bytes
+    // are unambiguously an ArrayBuffer-backed view at runtime, so a
+    // single cast is enough to satisfy NextResponse's BodyInit type.
+    const bytes = buildPlantHoursTemplateWorkbook(sample) as Uint8Array<ArrayBuffer>;
+    console.log(
+      `[plant-hours-template] size=${bytes.byteLength} duration_ms=${Date.now() - start}`,
+    );
+    return new NextResponse(bytes, {
+      status: 200,
+      headers: {
+        "Content-Type":
+          "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+        "Content-Disposition":
+          'attachment; filename="Plant_Hours_Template_2.xlsx"',
+        "Cache-Control": "no-store",
+      },
+    });
+  } catch (err) {
+    console.error(`[plant-hours-template] error:`, err);
+    return NextResponse.json(
+      { error: err instanceof Error ? err.message : "template_failed" },
+      { status: 500 },
+    );
+  }
+}