security: fix all Medium findings from FLAWS_REPORT audit

- Auth: TOTP replay protection with counter tracking, constant-time
  backup code comparison, atomic lockout increment, per-token logout
- Invoices/PDFs: net-based VAT calculation, dangerous URL scheme
  stripping in cleanQuillHtml, orders-pdf error handling
- Orders: reject item changes on status transition, cascading
  delete cleanup, take:1 with orderBy
- Projects: atomic rename collision handling, MIME/extension
  validation, empty customer name rejection
- Attendance: Czech public holiday awareness in frontend fund
  calculation, leave_hours 0 handling, invalid date NaN guard,
  bounded per-month queries in workfund
- Users/Admin: profile audit logging + password validation, session
  revocation guard, session ID validation, dashboard DB aggregation,
  soft-deleted record protection in scope templates
- Frontend: FormField label linkage, Pagination ARIA, error
  handling in OrderConfirmationModal, 401 propagation, GPS emoji
  hidden from screen readers, table sort state fix, geolocation
  race/abort cleanup, Leaflet popup DOM safety, Vehicles toggleActive
  minimal body, CompanySettings ref mutation fix, OfferDetail unlock
  abort, AttendanceBalances combined fetches
- Utils: env validation, Puppeteer concurrency mutex, invoice alert
  cron cleanup on shutdown, body limit alignment, TOTP error logging,
  trustProxy from env, symlink rejection, rate cache Map usage

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/schemas/customers.schema.ts

@@ -13,7 +13,7 @@ export const CreateCustomerSchema = z.object({
 });
 
 export const UpdateCustomerSchema = z.object({
-  name: z.string().optional(),
+  name: z.string().min(1, "Název zákazníka je povinný").optional(),
   street: z.string().nullish(),
   city: z.string().nullish(),
   postal_code: z.string().nullish(),

src/schemas/profile.schema.ts

@@ -5,7 +5,7 @@ export const UpdateProfileSchema = z.object({
   first_name: z.string().optional(),
   last_name: z.string().optional(),
   current_password: z.string().optional(),
-  new_password: z.string().optional(),
+  new_password: z.string().min(8, "Heslo musí mít alespoň 8 znaků").optional(),
 });
 
 export type UpdateProfileInput = z.infer<typeof UpdateProfileSchema>;