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/routes/admin/leave-requests.ts

@@ -205,7 +205,6 @@ export default async function leaveRequestsRoutes(
           }
         }
 
-        // Count business days and create attendance records
         let totalBusinessDays = 0;
         const current = new Date(dateFrom);
         const attendanceCreates: Array<{
@@ -242,7 +241,6 @@ export default async function leaveRequestsRoutes(
 
         const totalHours = totalBusinessDays * 8;
 
-        // Run everything in a transaction
         await prisma.$transaction(async (tx) => {
           // 1. Create attendance records for each business day
           if (attendanceCreates.length > 0) {