feat: CNB exchange rates, multi-currency KPI stats, invoice PDF VAT in CZK

- ČNB exchange rate service with date-specific rates and caching
- Invoice/received invoice stats convert foreign currencies to CZK
- Dashboard revenue converts all currencies to CZK
- Invoice PDF: VAT recap table always in CZK with CNB rate footer
- Inline styles replaced with utility classes (step 4 cleanup)
- Spinner animation exempt from prefers-reduced-motion

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

src/admin/pages/OfferDetail.tsx

@@ -180,9 +180,7 @@ function SortableItemRow({
           </button>
         </td>
       )}
-      <td style={{ textAlign: "center", color: "var(--text-tertiary)" }}>
-        {index + 1}
-      </td>
+      <td className="text-center text-tertiary">{index + 1}</td>
       <td style={{ verticalAlign: "top" }}>
         <div
           style={{ display: "flex", flexDirection: "column", gap: "0.25rem" }}
@@ -191,10 +189,9 @@ function SortableItemRow({
             type="text"
             value={item.description}
             onChange={(e) => onUpdate("description", e.target.value)}
-            className="admin-form-input"
+            className="admin-form-input fw-500"
             placeholder="Název položky"
             readOnly={readOnly}
-            style={{ fontWeight: 500 }}
           />
           <input
             type="text"
@@ -240,7 +237,7 @@ function SortableItemRow({
           readOnly={readOnly}
         />
       </td>
-      <td style={{ textAlign: "center" }}>
+      <td className="text-center">
         <input
           type="checkbox"
           checked={item.is_included_in_total}
@@ -248,10 +245,7 @@ function SortableItemRow({
           disabled={readOnly}
         />
       </td>
-      <td
-        className="admin-mono"
-        style={{ textAlign: "right", fontWeight: 600 }}
-      >
+      <td className="admin-mono text-right fw-600">
         {formatCurrency(lineTotal, currency)}
       </td>
       {!readOnly && (
@@ -874,11 +868,10 @@ export default function OfferDetail() {
               {isEdit ? `Nabídka ${form.quotation_number}` : "Nová nabídka"}
               {isInvalidated && (
                 <span
-                  className="admin-badge admin-badge-danger"
+                  className="admin-badge admin-badge-danger text-xs"
                   style={{
                     marginLeft: "0.75rem",
                     verticalAlign: "middle",
-                    fontSize: "0.75rem",
                   }}
                 >
                   Zneplatněna
@@ -1208,10 +1201,7 @@ export default function OfferDetail() {
                     </option>
                   ))}
                 </select>
-                <label
-                  className="admin-form-checkbox"
-                  style={{ whiteSpace: "nowrap" }}
-                >
+                <label className="admin-form-checkbox whitespace-nowrap">
                   <input
                     type="checkbox"
                     checked={form.apply_vat}
@@ -1672,7 +1662,7 @@ export default function OfferDetail() {
                   <FormField label="Příloha (PDF)">
                     {orderAttachment ? (
                       <div className="flex-row gap-2">
-                        <span style={{ fontSize: "0.875rem" }}>
+                        <span className="text-md">
                           {orderAttachment.name}{" "}
                           <span className="text-tertiary">
                             ({(orderAttachment.size / 1024).toFixed(0)} KB)