feat(reader): remember reading position across refresh, add chapter progress bar, and plan PDF support

app/static/css/style.css

@@ -3137,6 +3137,41 @@ body {
     max-width: 240px;
 }
 
+.reader-progress-badge {
+    font-size: 11px;
+    font-weight: 700;
+    font-variant-numeric: tabular-nums;
+    color: var(--primary);
+    background: var(--primary-dim);
+    border: 1px solid rgba(56, 189, 248, 0.35);
+    padding: 3px 8px;
+    border-radius: var(--radius-full);
+    min-width: 40px;
+    text-align: center;
+    display: inline-block;
+    user-select: none;
+    line-height: 1.2;
+}
+
+.reader-chapter-progress-bar {
+    position: absolute;
+    left: 0;
+    right: 0;
+    bottom: -1px;
+    height: 3px;
+    background-color: rgba(255, 255, 255, 0.08);
+    overflow: hidden;
+    pointer-events: none;
+}
+
+.reader-chapter-progress-fill {
+    height: 100%;
+    width: 0%;
+    background: linear-gradient(90deg, #0284c7, #38bdf8);
+    box-shadow: 0 0 8px rgba(56, 189, 248, 0.5);
+    transition: width 0.12s cubic-bezier(0.16, 1, 0.3, 1);
+}
+
 .reader-toolbar-right {
     display: flex;
     align-items: center;