feat: NAS storage for invoices/offers, code cleanup, date/time fixes

- NAS storage for created invoices (PDF via puppeteer), received invoices,
  and offers with auto-save on create/edit
- Deterministic file paths derived from DB fields (no file_path column needed)
- Separate NAS mount points: NAS_FINANCIALS_PATH, NAS_OFFERS_PATH
- Invoice language field (cs/en) stored per invoice, replaces lang modal
- Invoices list filtered by month/year matching KPI card selection
- Centralized date helpers (src/utils/date.ts) replacing all .toISOString()
  calls that returned UTC instead of local time
- Attendance project switching uses exact time (not rounded)
- Comment cleanup: removed ~100 unnecessary/Czech comments
- Removed as-any casts in orders and attendance
- Prisma migrations: add invoice language, drop received_invoices BLOB columns

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

src/utils/czech-holidays.ts

@@ -3,6 +3,8 @@
  * Port of PHP CzechHolidays class.
  */
 
+import { localDateStr } from "./date";
+
 const holidayCache = new Map<number, string[]>();
 
 /** Easter Sunday using the Anonymous Gregorian algorithm */
@@ -30,17 +32,17 @@ export function getHolidays(year: number): string[] {
 
   const y = String(year);
   const holidays = [
-    `${y}-01-01`, // Den obnovy samostatného českého státu
-    `${y}-05-01`, // Svátek práce
-    `${y}-05-08`, // Den vítězství
-    `${y}-07-05`, // Den slovanských věrozvěstů Cyrila a Metoděje
-    `${y}-07-06`, // Den upálení mistra Jana Husa
-    `${y}-09-28`, // Den české státnosti
-    `${y}-10-28`, // Den vzniku samostatného československého státu
-    `${y}-11-17`, // Den boje za svobodu a demokracii
-    `${y}-12-24`, // Štědrý den
-    `${y}-12-25`, // 1. svátek vánoční
-    `${y}-12-26`, // 2. svátek vánoční
+    `${y}-01-01`, // New Year's / Restoration of Czech Independence
+    `${y}-05-01`, // Labour Day
+    `${y}-05-08`, // Victory Day
+    `${y}-07-05`, // Saints Cyril and Methodius Day
+    `${y}-07-06`, // Jan Hus Day
+    `${y}-09-28`, // Czech Statehood Day
+    `${y}-10-28`, // Czechoslovak Independence Day
+    `${y}-11-17`, // Freedom and Democracy Day
+    `${y}-12-24`, // Christmas Eve
+    `${y}-12-25`, // Christmas Day
+    `${y}-12-26`, // St. Stephen's Day
   ];
 
   // Easter-based
@@ -51,10 +53,8 @@ export function getHolidays(year: number): string[] {
   const easterMonday = new Date(easterDate);
   easterMonday.setDate(easterMonday.getDate() + 1);
 
-  const fmt = (d: Date) =>
-    `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}-${String(d.getDate()).padStart(2, "0")}`;
-  holidays.push(fmt(goodFriday)); // Velký pátek
-  holidays.push(fmt(easterMonday)); // Velikonoční pondělí
+  holidays.push(localDateStr(goodFriday)); // Good Friday
+  holidays.push(localDateStr(easterMonday)); // Easter Monday
 
   holidays.sort();
   holidayCache.set(year, holidays);

src/utils/date.ts

@@ -0,0 +1,40 @@
+/**
+ * Centralized date/time helpers.
+ *
+ * Prisma stores DateTime as UTC in MySQL DATETIME columns.
+ * The Date.toJSON override in config/env.ts serializes using local getters,
+ * so the frontend always receives local time. These helpers ensure
+ * consistent local-time formatting whenever we need a string outside
+ * of JSON serialization (e.g., building lookup keys, shift_date strings).
+ */
+
+/** YYYY-MM-DD in local time */
+export function localDateStr(d: Date): string {
+  const y = d.getFullYear();
+  const m = String(d.getMonth() + 1).padStart(2, "0");
+  const day = String(d.getDate()).padStart(2, "0");
+  return `${y}-${m}-${day}`;
+}
+
+/** YYYY-MM in local time */
+export function localMonthStr(d: Date): string {
+  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}`;
+}
+
+/** HH:MM in local time */
+export function localTimeStr(d: Date): string {
+  return `${String(d.getHours()).padStart(2, "0")}:${String(d.getMinutes()).padStart(2, "0")}`;
+}
+
+/** DD.MM.YYYY in local time (Czech date format) */
+export function localDateCzStr(d: Date): string {
+  return `${String(d.getDate()).padStart(2, "0")}.${String(d.getMonth() + 1).padStart(2, "0")}.${d.getFullYear()}`;
+}
+
+/** DD.MM.YYYY HH:MM:SS in local time (Czech datetime format) */
+export function localDateTimeCzStr(d: Date): string {
+  const h = String(d.getHours()).padStart(2, "0");
+  const min = String(d.getMinutes()).padStart(2, "0");
+  const s = String(d.getSeconds()).padStart(2, "0");
+  return `${localDateCzStr(d)} ${h}:${min}:${s}`;
+}

src/utils/html-to-pdf.ts

@@ -0,0 +1,52 @@
+import { Browser } from "puppeteer";
+
+let browser: Browser | null = null;
+
+async function getBrowser(): Promise<Browser> {
+  if (browser && browser.connected) return browser;
+
+  // Try puppeteer (bundles Chromium), fall back to puppeteer-core (system Chromium)
+  try {
+    const puppeteer = await import("puppeteer");
+    browser = await puppeteer.default.launch({
+      headless: true,
+      args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-gpu"],
+    });
+  } catch {
+    const core = await import("puppeteer-core");
+    const executablePath =
+      process.env.CHROMIUM_PATH ||
+      "/usr/bin/chromium-browser" ||
+      "/usr/bin/chromium";
+    browser = await core.default.launch({
+      headless: true,
+      executablePath,
+      args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-gpu"],
+    });
+  }
+
+  return browser;
+}
+
+export async function htmlToPdf(html: string): Promise<Buffer> {
+  const b = await getBrowser();
+  const page = await b.newPage();
+  try {
+    await page.setContent(html, { waitUntil: "networkidle0" });
+    const pdf = await page.pdf({
+      format: "A4",
+      printBackground: true,
+      margin: { top: "10mm", bottom: "10mm", left: "10mm", right: "10mm" },
+    });
+    return Buffer.from(pdf);
+  } finally {
+    await page.close();
+  }
+}
+
+export async function closeBrowser(): Promise<void> {
+  if (browser) {
+    await browser.close();
+    browser = null;
+  }
+}