refactor: P3 dekompozice velkych komponent

Dashboard.jsx (1346 -> 378 LOC):
- DashKpiCards, DashQuickActions, DashActivityFeed, DashAttendanceToday, DashProfile, DashSessions
- dashboardHelpers.js (konstanty + helper funkce)

OfferDetail.jsx (1061 -> ~530 LOC):
- useOfferForm hook (form state, draft, items/sections, submit)
- OfferCustomerPicker (customer search/select dropdown)

AttendanceAdmin.jsx (1036 -> ~275 LOC):
- useAttendanceAdmin hook (data fetching, filters, CRUD, print)
- AttendanceShiftTable (shift records table)

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

src/admin/components/OfferCustomerPicker.jsx

@@ -0,0 +1,90 @@
+import { useState, useEffect, useMemo } from 'react'
+
+export default function OfferCustomerPicker({
+  customers,
+  customerId,
+  customerName,
+  onSelect,
+  onClear,
+  error,
+  readOnly
+}) {
+  const [customerSearch, setCustomerSearch] = useState('')
+  const [showDropdown, setShowDropdown] = useState(false)
+
+  // Close dropdown on outside click
+  useEffect(() => {
+    const handleClickOutside = () => setShowDropdown(false)
+    if (showDropdown) {
+      document.addEventListener('click', handleClickOutside)
+      return () => document.removeEventListener('click', handleClickOutside)
+    }
+  }, [showDropdown])
+
+  const filteredCustomers = useMemo(() => {
+    if (!customerSearch) return customers
+    const q = customerSearch.toLowerCase()
+    return customers.filter(c =>
+      (c.name || '').toLowerCase().includes(q) ||
+      (c.company_id || '').includes(customerSearch) ||
+      (c.city || '').toLowerCase().includes(q)
+    )
+  }, [customers, customerSearch])
+
+  const handleSelect = (customer) => {
+    onSelect(customer)
+    setCustomerSearch('')
+    setShowDropdown(false)
+  }
+
+  return (
+    <div className={`admin-form-group${error ? ' has-error' : ''}`}>
+      <label className="admin-form-label required">Zákazník</label>
+      {customerId && (
+        <div className="offers-customer-selected">
+          <span>{customerName}</span>
+          {!readOnly && (
+            <button type="button" onClick={onClear} className="admin-btn-icon" title="Odebrat zákazníka" aria-label="Odebrat zákazníka">
+              <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
+                <line x1="18" y1="6" x2="6" y2="18" /><line x1="6" y1="6" x2="18" y2="18" />
+              </svg>
+            </button>
+          )}
+        </div>
+      )}
+      {!customerId && !readOnly && (
+        <div className="offers-customer-select" onClick={(e) => e.stopPropagation()}>
+          <input
+            type="text"
+            value={customerSearch}
+            onChange={(e) => { setCustomerSearch(e.target.value); setShowDropdown(true) }}
+            onFocus={() => setShowDropdown(true)}
+            className="admin-form-input"
+            placeholder="Hledat zákazníka..."
+          />
+          {showDropdown && (
+            <div className="offers-customer-dropdown">
+              {filteredCustomers.length === 0 ? (
+                <div className="offers-customer-dropdown-empty">
+                  Žádní zákazníci
+                </div>
+              ) : (
+                filteredCustomers.slice(0, 10).map(c => (
+                  <div
+                    key={c.id}
+                    className="offers-customer-dropdown-item"
+                    onMouseDown={() => handleSelect(c)}
+                  >
+                    <div>{c.name}</div>
+                    {c.city && <div>{c.city}</div>}
+                  </div>
+                ))
+              )}
+            </div>
+          )}
+        </div>
+      )}
+      {error && <span className="admin-form-error">{error}</span>}
+    </div>
+  )
+}