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);