feat(a11y): ARIA labels, focus management, skip-nav, keyboard nav, contrast fix

Accessibility improvements per WCAG 2.1 AA:
- Skip-to-content link (TA-1)
- ARIA landmarks and roles for nav, main, sections, footer (TA-2)
- Accordion keyboard navigation + aria-expanded (TA-3)
- Lightbox focus trap + focus management + dialog role (TA-4)
- Gallery grid items keyboard accessible (TA-5)
- Improved alt texts for all images (TA-6)
- Focus-visible styles for all interactive elements (TA-7)
- Darker --stone color for WCAG AA contrast compliance (TA-8)

Fix #18

js/haus-schleusingen.js

@@ -36,38 +36,104 @@ $(function () {
     var item = $(this).closest(".floor-item");
     var isOpen = item.hasClass("open");
     $(".floor-item").removeClass("open");
+    $(".floor-header").attr("aria-expanded", "false");
     $(".floor-body").slideUp(300);
     if (!isOpen) {
       item.addClass("open");
+      $(this).attr("aria-expanded", "true");
       item.find(".floor-body").slideDown(300);
     }
   });
 
+  // Accordion keyboard handler (Enter/Space)
+  $(".floor-header").on("keydown", function (e) {
+    if (e.key === "Enter" || e.key === " ") {
+      e.preventDefault();
+      $(this).trigger("click");
+    }
+  });
+
+  // Lightbox – track last focused element for focus return
+  var lightboxTrigger = null;
+
+  function openLightbox(src) {
+    lightboxTrigger = document.activeElement;
+    $("#lightboxImg").attr("src", src).attr("alt", "");
+    $("#lightbox").addClass("open");
+    $("body").css("overflow", "hidden");
+    // Set focus to close button
+    setTimeout(function () {
+      $("#lightboxClose").focus();
+    }, 50);
+  }
+
+  function closeLightbox() {
+    $("#lightbox").removeClass("open");
+    $("body").css("overflow", "");
+    // Return focus to trigger
+    if (lightboxTrigger) {
+      $(lightboxTrigger).focus();
+      lightboxTrigger = null;
+    }
+  }
+
   // Lightbox – gallery grid items
   $(document).on("click", ".grid-item", function () {
     var src = $(this).data("img") || $(this).find("img").attr("src");
-    $("#lightboxImg").attr("src", src);
-    $("#lightbox").addClass("open");
-    $("body").css("overflow", "hidden");
+    openLightbox(src);
   });
 
   // Lightbox – floor plan images in Raumaufteilung
   $(document).on("click", ".floor-plan img[data-img]", function () {
     var src = $(this).data("img");
-    $("#lightboxImg").attr("src", src);
-    $("#lightbox").addClass("open");
-    $("body").css("overflow", "hidden");
+    openLightbox(src);
   });
-  $("#lightboxClose, #lightbox").on("click", function (e) {
+
+  // Lightbox close handlers
+  $("#lightboxClose").on("click", function () {
+    closeLightbox();
+  });
+  $("#lightbox").on("click", function (e) {
     if (e.target === this) {
-      $("#lightbox").removeClass("open");
-      $("body").css("overflow", "");
+      closeLightbox();
     }
   });
+
+  // Escape key to close lightbox
   $(document).on("keydown", function (e) {
-    if (e.key === "Escape") {
-      $("#lightbox").removeClass("open");
-      $("body").css("overflow", "");
+    if (e.key === "Escape" && $("#lightbox").hasClass("open")) {
+      closeLightbox();
+    }
+  });
+
+  // Focus trap for lightbox
+  $("#lightbox").on("keydown", function (e) {
+    if (e.key !== "Tab") return;
+
+    var focusable = $(this).find("button, [href], input, select, textarea, [tabindex]:not([tabindex='-1'])").filter(":visible");
+    if (focusable.length === 0) return;
+
+    var first = focusable[0];
+    var last = focusable[focusable.length - 1];
+
+    if (e.shiftKey) {
+      if (document.activeElement === first) {
+        e.preventDefault();
+        last.focus();
+      }
+    } else {
+      if (document.activeElement === last) {
+        e.preventDefault();
+        first.focus();
+      }
+    }
+  });
+
+  // Gallery keyboard handler (Enter/Space)
+  $(document).on("keydown", ".grid-item", function (e) {
+    if (e.key === "Enter" || e.key === " ") {
+      e.preventDefault();
+      $(this).trigger("click");
     }
   });