refactor: CSS utility tridy + slouceni badge souboru

- pridano 20 utility trid (flex-1, mb-2, text-right, fw-500, admin-spinner-sm, atd.)
- nahrazeno ~100 opakovanych inline stylu ve 39 JSX souborech
- slouceno leave.css, orders.css, projects.css do admin.css (status badges)
- bundle size: 228.91 -> 228.43 kB (-0.48 kB)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/admin/pages/Invoices.jsx

@@ -313,7 +313,7 @@ export default function Invoices() {
           </button>
         </div>
 
-        <div className="offers-tabs" style={{ marginBottom: '1rem', justifyContent: 'center' }}>
+        <div className="offers-tabs mb-4" style={{ justifyContent: 'center' }}>
           <button className={`offers-tab ${activeTab === 'issued' ? 'active' : ''}`} onClick={() => setActiveTab('issued')}>
             Vydané
           </button>
@@ -427,7 +427,7 @@ export default function Invoices() {
         animate={{ opacity: 1, y: 0 }}
         transition={{ duration: 0.4, delay: 0.2 }}
       >
-        <div className="offers-tabs" style={{ marginBottom: '1.5rem' }}>
+        <div className="offers-tabs mb-6">
           {STATUS_FILTERS.map(f => (
             <button
               key={f.value}
@@ -448,7 +448,7 @@ export default function Invoices() {
         transition={{ duration: 0.4, delay: 0.25 }}
       >
         <div className="admin-card-body">
-          <div className="admin-search-bar" style={{ marginBottom: '1rem' }}>
+          <div className="admin-search-bar mb-4">
             <input
               type="text"
               value={search}
@@ -494,7 +494,7 @@ export default function Invoices() {
                     <th style={{ cursor: 'pointer' }} onClick={() => handleSort('due_date')}>
                       Splatnost <SortIcon column="due_date" sort={activeSort} order={order} />
                     </th>
-                    <th style={{ textAlign: 'right' }}>Celkem</th>
+                    <th className="text-right">Celkem</th>
                     <th>Akce</th>
                   </tr>
                 </thead>