feat: invoice due date email alerts, add favicon

- Daily cron (8:00 AM) checks created and received invoices
- Alerts 3 days before due date and on due date
- Summary email to INVOICE_ALERT_EMAIL with grouped tables
- Tracks sent alerts in invoice_alert_log to prevent duplicates
- node-cron scheduler runs inside the app process
- Favicon files copied from PHP project

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/services/invoice-alerts.ts

@@ -0,0 +1,227 @@
+import prisma from "../config/database";
+import { config } from "../config/env";
+import { sendMail } from "./mailer";
+import { localDateCzStr, localDateStr } from "../utils/date";
+
+interface AlertInvoice {
+  id: number;
+  type: "created" | "received";
+  number: string;
+  counterparty: string;
+  amount: string;
+  currency: string;
+  due_date: string;
+  days_label: string;
+}
+
+function escapeHtml(str: string): string {
+  return str
+    .replace(/&/g, "&")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/"/g, "&quot;");
+}
+
+function formatAmount(n: number | { toNumber?: () => number }): string {
+  const num = typeof n === "number" ? n : Number(n);
+  return num.toLocaleString("cs-CZ", {
+    minimumFractionDigits: 2,
+    maximumFractionDigits: 2,
+  });
+}
+
+export async function checkInvoiceAlerts(): Promise<void> {
+  const alertEmail = config.email.invoiceAlert;
+  if (!alertEmail) return;
+
+  const today = new Date();
+  const todayStr = localDateStr(today);
+  const in3days = new Date(today);
+  in3days.setDate(in3days.getDate() + 3);
+  const in3daysStr = localDateStr(in3days);
+
+  const alerts: AlertInvoice[] = [];
+
+  // --- Created invoices (customer owes us) ---
+  const createdInvoices = await prisma.invoices.findMany({
+    where: {
+      status: { in: ["issued", "overdue"] },
+      due_date: { not: null },
+    },
+    include: {
+      customers: { select: { name: true } },
+      invoice_items: true,
+    },
+  });
+
+  for (const inv of createdInvoices) {
+    if (!inv.due_date) continue;
+    const dueDateStr = localDateStr(new Date(inv.due_date));
+
+    let alertType: string | null = null;
+    let daysLabel = "";
+
+    if (dueDateStr === todayStr) {
+      alertType = "due";
+      daysLabel = "splatnost dnes";
+    } else if (dueDateStr === in3daysStr) {
+      alertType = "3days";
+      daysLabel = "splatnost za 3 dny";
+    }
+
+    if (!alertType) continue;
+
+    const alreadySent = await prisma.invoice_alert_log.findUnique({
+      where: {
+        invoice_type_invoice_id_alert_type: {
+          invoice_type: "created",
+          invoice_id: inv.id,
+          alert_type: alertType,
+        },
+      },
+    });
+    if (alreadySent) continue;
+
+    const subtotal = inv.invoice_items.reduce(
+      (sum, item) => sum + Number(item.quantity) * Number(item.unit_price),
+      0,
+    );
+
+    alerts.push({
+      id: inv.id,
+      type: "created",
+      number: inv.invoice_number || `#${inv.id}`,
+      counterparty: inv.customers?.name || "—",
+      amount: formatAmount(subtotal),
+      currency: inv.currency || "CZK",
+      due_date: localDateCzStr(new Date(inv.due_date)),
+      days_label: daysLabel,
+    });
+
+    await prisma.invoice_alert_log.create({
+      data: {
+        invoice_type: "created",
+        invoice_id: inv.id,
+        alert_type: alertType,
+      },
+    });
+  }
+
+  // --- Received invoices (we owe supplier) ---
+  const receivedInvoices = await prisma.received_invoices.findMany({
+    where: {
+      status: "unpaid",
+      due_date: { not: null },
+    },
+  });
+
+  for (const inv of receivedInvoices) {
+    if (!inv.due_date) continue;
+    const dueDateStr = localDateStr(new Date(inv.due_date));
+
+    let alertType: string | null = null;
+    let daysLabel = "";
+
+    if (dueDateStr === todayStr) {
+      alertType = "due";
+      daysLabel = "splatnost dnes";
+    } else if (dueDateStr === in3daysStr) {
+      alertType = "3days";
+      daysLabel = "splatnost za 3 dny";
+    }
+
+    if (!alertType) continue;
+
+    const alreadySent = await prisma.invoice_alert_log.findUnique({
+      where: {
+        invoice_type_invoice_id_alert_type: {
+          invoice_type: "received",
+          invoice_id: inv.id,
+          alert_type: alertType,
+        },
+      },
+    });
+    if (alreadySent) continue;
+
+    alerts.push({
+      id: inv.id,
+      type: "received",
+      number: inv.invoice_number || inv.supplier_name,
+      counterparty: inv.supplier_name,
+      amount: formatAmount(inv.amount),
+      currency: inv.currency,
+      due_date: localDateCzStr(new Date(inv.due_date)),
+      days_label: daysLabel,
+    });
+
+    await prisma.invoice_alert_log.create({
+      data: {
+        invoice_type: "received",
+        invoice_id: inv.id,
+        alert_type: alertType,
+      },
+    });
+  }
+
+  if (alerts.length === 0) return;
+
+  // --- Build summary email ---
+  const createdAlerts = alerts.filter((a) => a.type === "created");
+  const receivedAlerts = alerts.filter((a) => a.type === "received");
+
+  const subject = `Upozornění na splatnost faktur (${alerts.length})`;
+
+  const buildTable = (items: AlertInvoice[], title: string) => {
+    if (items.length === 0) return "";
+    const rows = items
+      .map(
+        (a) => `
+        <tr>
+          <td style="padding: 8px; border-bottom: 1px solid #ddd;">${escapeHtml(a.number)}</td>
+          <td style="padding: 8px; border-bottom: 1px solid #ddd;">${escapeHtml(a.counterparty)}</td>
+          <td style="padding: 8px; border-bottom: 1px solid #ddd; text-align: right;">${a.amount} ${a.currency}</td>
+          <td style="padding: 8px; border-bottom: 1px solid #ddd;">${a.due_date}</td>
+          <td style="padding: 8px; border-bottom: 1px solid #ddd; color: ${a.days_label.includes("dnes") ? "#dc3545" : "#e67e22"}; font-weight: bold;">${a.days_label}</td>
+        </tr>`,
+      )
+      .join("");
+
+    return `
+      <h3 style="color: #333; margin-top: 24px;">${escapeHtml(title)} (${items.length})</h3>
+      <table style="width: 100%; border-collapse: collapse; margin: 12px 0;">
+        <thead>
+          <tr style="background: #f5f5f5;">
+            <th style="padding: 8px; text-align: left;">Číslo</th>
+            <th style="padding: 8px; text-align: left;">Firma</th>
+            <th style="padding: 8px; text-align: right;">Částka</th>
+            <th style="padding: 8px; text-align: left;">Splatnost</th>
+            <th style="padding: 8px; text-align: left;">Stav</th>
+          </tr>
+        </thead>
+        <tbody>${rows}</tbody>
+      </table>`;
+  };
+
+  const html = `
+    <html>
+    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
+      <h2 style="color: #dc3545;">Upozornění na splatnost faktur</h2>
+      <p>Následující faktury se blíží ke splatnosti nebo jsou dnes splatné:</p>
+      ${buildTable(createdAlerts, "Vydané faktury (neuhrazené zákazníkem)")}
+      ${buildTable(receivedAlerts, "Přijaté faktury (k úhradě)")}
+      <hr style="margin: 30px 0; border: none; border-top: 1px solid #ddd;">
+      <p style="font-size: 12px; color: #999;">
+        Automatické upozornění vygenerováno ${localDateCzStr(today)}.
+      </p>
+    </body>
+    </html>`;
+
+  const sent = await sendMail(alertEmail, subject, html);
+  if (!sent) {
+    console.error(`InvoiceAlerts: Failed to send alert to ${alertEmail}`);
+  } else {
+    console.log(
+      `InvoiceAlerts: Sent ${alerts.length} alert(s) to ${alertEmail}`,
+    );
+  }
+}