feat(v0.1): historia cen + jawnosc cen — milestone Initial Release

Historia cen:
- Tabela wp_price_history z WP Cronem dziennym (snapshot cen)
- AJAX endpoint apartamenty_get_price_history (zabezpieczony nonce)
- Popup "Historia cen" w widgecie — vanilla JS, modal zgodny z projektem

Jawnosc cen:
- Endpointy /ceny-mieszkan.xml + /dane-gov-pl.xml (XSD-compliant)
- Pliki MD5 dla obu XML
- Strona admina: Narzedzia -> Jawnosc Cen z URL-ami do Ministerstwa
- Transient cache 1h z inwalidacja przez cron

Dokumentacja: docs/readme.md + docs/jawnosc-cen.md

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

wp-content/plugins/elementor-addon/assets/js/main.js

@@ -18,3 +18,109 @@ document.addEventListener('DOMContentLoaded', function () {
         hideClass: 'fancybox-fadeOut',
     });
 });
+
+// Historia cen
+document.addEventListener('DOMContentLoaded', function () {
+    var overlay  = document.getElementById('price-history-overlay');
+    var closeBtn = document.getElementById('price-history-close');
+    var elTitle  = document.getElementById('price-history-title');
+    var elPrice  = document.getElementById('price-history-price');
+    var elPriceM2= document.getElementById('price-history-sqm');
+    var elTbody  = document.getElementById('price-history-tbody');
+
+    if (!overlay || !closeBtn || !elTitle || !elPrice || !elPriceM2 || !elTbody) {
+        console.warn('[historia-cen] Brakuje elementów popupa w DOM:', {
+            overlay: !!overlay, closeBtn: !!closeBtn,
+            elTitle: !!elTitle, elPrice: !!elPrice,
+            elPriceM2: !!elPriceM2, elTbody: !!elTbody
+        });
+        return;
+    }
+
+    function openPopup() {
+        overlay.setAttribute('aria-hidden', 'false');
+        overlay.classList.add('is-open');
+        document.body.style.overflow = 'hidden';
+    }
+
+    function closePopup() {
+        overlay.setAttribute('aria-hidden', 'true');
+        overlay.classList.remove('is-open');
+        document.body.style.overflow = '';
+    }
+
+    // Zamknij przyciskiem X
+    closeBtn.addEventListener('click', closePopup);
+
+    // Zamknij klikając na overlay (poza modalem)
+    overlay.addEventListener('click', function (e) {
+        if (e.target === overlay) closePopup();
+    });
+
+    // Zamknij klawiszem Escape
+    document.addEventListener('keydown', function (e) {
+        if (e.key === 'Escape' && overlay.classList.contains('is-open')) closePopup();
+    });
+
+    // Kliknięcie w przycisk Historia cen
+    document.querySelectorAll('.btn-historia-cen').forEach(function (btn) {
+        btn.addEventListener('click', function () {
+            var postId = this.dataset.postId;
+            if (!postId) return;
+
+            // Reset i pokaż "Ładowanie..."
+            elTitle.textContent   = 'Ładowanie...';
+            elPrice.textContent   = '';
+            elPriceM2.textContent = '';
+            elTbody.innerHTML     = '';
+            openPopup();
+
+            // Sprawdź dostępność danych globalnych (wp_localize_script)
+            if (typeof apartamentsData === 'undefined') {
+                elTitle.textContent = 'Błąd konfiguracji';
+                return;
+            }
+
+            // Buduj FormData
+            var formData = new FormData();
+            formData.append('action',  'apartamenty_get_price_history');
+            formData.append('post_id', postId);
+            formData.append('nonce',   apartamentsData.nonce);
+
+            fetch(apartamentsData.ajaxUrl, {
+                method: 'POST',
+                body: formData,
+                credentials: 'same-origin',
+            })
+            .then(function (res) { return res.json(); })
+            .then(function (json) {
+                if (!json.success) {
+                    elTitle.textContent = 'Brak danych';
+                    return;
+                }
+
+                var d = json.data;
+
+                elTitle.textContent   = d.title || '';
+                elPrice.textContent   = d.price   ? d.price   + ' zł' : '—';
+                elPriceM2.textContent = d.price_m2 ? d.price_m2 + ' zł' : '—';
+
+                if (!d.history || d.history.length === 0) {
+                    elTbody.innerHTML = '<tr><td colspan="3">Brak historii cen</td></tr>';
+                    return;
+                }
+
+                elTbody.innerHTML = d.history.map(function (row) {
+                    return '<tr>' +
+                        '<td>' + (row.recorded_at || '') + '</td>' +
+                        '<td>' + (row.price_m2 ? row.price_m2 + ' zł/m²' : '—') + '</td>' +
+                        '<td>' + (row.price ? row.price + ' zł' : '—') + '</td>' +
+                    '</tr>';
+                }).join('');
+            })
+            .catch(function () {
+                elTitle.textContent = 'Błąd ładowania';
+            });
+        });
+    });
+});