fix(ui): unify list filters across all pages (bare controls, standard sizes)

Every list-page FilterBar now follows one spec: bare controls (no Field label rows — which broke flex-end alignment), standardized widths (search 1 1 320px grows; small selects 0 0 160px; entity selects 0 0 220px; MonthField 0 0 180px; dates 0 0 150px), consistent 'Všechny/Všichni/Všechna <entity>' defaults, and a placeholder on every search. TripsAdmin's separate month-Select + year-Select collapse into one MonthField (yyyy-MM, split at the query boundary) — matching Attendance/TripsHistory. The 4 labeled attendance/trips pages move off the Field wrapper; Projects & ReceivedInvoices move their inline search into a FilterBar. Chrome-verified all ~18 filter pages in light + the existing theme.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/WarehouseReceipts.tsx

@@ -182,7 +182,7 @@ export default function WarehouseReceipts() {
       />
 
       <FilterBar>
-        <Box sx={{ flex: "1 1 220px" }}>
+        <Box sx={{ flex: "1 1 320px" }}>
           <TextField
             value={search}
             onChange={(e) => {
@@ -209,7 +209,7 @@ export default function WarehouseReceipts() {
           />
         </Box>
         {suppliers.length > 0 && (
-          <Box sx={{ flex: "0 0 200px" }}>
+          <Box sx={{ flex: "0 0 220px" }}>
             <Select
               value={supplierId === "" ? "" : String(supplierId)}
               onChange={(val) => {