feat: toast notification + button flash on bookmark add

- showToast() displays a centered bottom toast for 3s
- flashBookmarkBtn() pulses the 🔖 button on bookmark creation
- CSS: .reader-toast with slide-up fade-in/out animation
- CSS: .bm-flash with @keyframes bmPulse (scale 1→1.25→1)
- user gets clear feedback when bookmark is saved

bookish/static/css/style.css

@@ -593,6 +593,42 @@ body {
     border-radius: 4px;
 }
 
+/* Toast notification */
+.reader-toast {
+    position: fixed;
+    bottom: 24px;
+    left: 50%;
+    transform: translateX(-50%) translateY(20px);
+    background: #1d1d1f;
+    color: #fff;
+    padding: 0.7rem 1.4rem;
+    border-radius: 10px;
+    font-size: 0.85rem;
+    box-shadow: 0 4px 20px rgba(0,0,0,0.25);
+    z-index: 300;
+    opacity: 0;
+    transition: opacity 0.3s, transform 0.3s;
+    pointer-events: none;
+    white-space: nowrap;
+}
+
+.reader-toast.show {
+    opacity: 1;
+    transform: translateX(-50%) translateY(0);
+}
+
+/* Bookmark button flash */
+.bm-flash {
+    animation: bmPulse 0.6s ease;
+}
+
+@keyframes bmPulse {
+    0%   { transform: scale(1); }
+    30%  { transform: scale(1.25); color: #007aff; }
+    60%  { transform: scale(1); }
+    100% { transform: scale(1); }
+}
+
 /* Reader Layout */
 .reader-container {
     display: flex;

bookish/static/js/reader.js

@@ -713,6 +713,17 @@
         bookmarks.push(data);
         saveBookmarks(bookmarks);
         renderBookmarks();
+
+        // Feedback visivo
+        flashBookmarkBtn();
+        showToast("Segnalibro aggiunto — vedi la scheda Segnalibri nella sidebar");
+    }
+
+    function flashBookmarkBtn() {
+        const btn = document.getElementById("bookmarkToggle");
+        if (!btn) return;
+        btn.classList.add("bm-flash");
+        setTimeout(() => btn.classList.remove("bm-flash"), 600);
     }
 
     function removeBookmark(id) {
@@ -778,6 +789,26 @@
         });
     }
 
+    // === Toast notifications ===
+
+    function showToast(msg) {
+        const existing = document.querySelector(".reader-toast");
+        if (existing) existing.remove();
+
+        const toast = document.createElement("div");
+        toast.className = "reader-toast";
+        toast.textContent = msg;
+        document.body.appendChild(toast);
+
+        // Trigger animation
+        requestAnimationFrame(() => toast.classList.add("show"));
+
+        setTimeout(() => {
+            toast.classList.remove("show");
+            setTimeout(() => toast.remove(), 300);
+        }, 3000);
+    }
+
     // === Utils ===
     function debounce(fn, ms) {
         let timer;