feat: add search and sort to thoughts detail page

- Search box: real-time filter across highlights, book reviews, and
  thoughts content (mark_text, content, abstract fields)
- Sort dropdown: 3 modes - newest first, oldest first, by chapter order
  (chapter_uid + range position)
- Chapter sort mode groups highlights by chapter with titles
- Time sort mode flattens highlights with chapter labels
- Empty state shows search keyword when no results match
- Mobile responsive: toolbar stacks vertically on narrow screens

static/css/style.css

@@ -1543,14 +1543,70 @@ body {
     color: var(--accent-dark);
 }
 
-/* 想法页面分类筛选 */
+/* 想法页面工具栏 */
+.thoughts-toolbar {
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    gap: 12px;
+    margin: 24px 0 20px;
+    flex-wrap: wrap;
+}
+
 .thoughts-filters {
     display: flex;
     gap: 8px;
-    margin: 24px 0 20px;
     flex-wrap: wrap;
 }
 
+.thoughts-controls {
+    display: flex;
+    gap: 10px;
+    align-items: center;
+}
+
+.thoughts-search-input {
+    padding: 7px 14px;
+    border: 1px solid var(--border);
+    border-radius: 20px;
+    background: var(--bg-card);
+    color: var(--text-primary);
+    font-size: 14px;
+    width: 240px;
+    transition: border-color 0.2s, box-shadow 0.2s;
+    outline: none;
+}
+
+.thoughts-search-input:focus {
+    border-color: var(--accent);
+    box-shadow: 0 0 0 3px var(--accent-bg);
+}
+
+.thoughts-search-input::placeholder {
+    color: var(--text-light);
+}
+
+.thoughts-sort-select {
+    padding: 7px 14px;
+    border: 1px solid var(--border);
+    border-radius: 20px;
+    background: var(--bg-card);
+    color: var(--text-primary);
+    font-size: 14px;
+    cursor: pointer;
+    outline: none;
+    transition: border-color 0.2s;
+}
+
+.thoughts-sort-select:hover {
+    border-color: var(--accent);
+}
+
+.thoughts-sort-select:focus {
+    border-color: var(--accent);
+    box-shadow: 0 0 0 3px var(--accent-bg);
+}
+
 .thought-filter-btn {
     padding: 6px 18px;
     border: 1px solid var(--border);
@@ -1830,6 +1886,20 @@ body {
     .global-search-wrapper {
         max-width: 100%;
     }
+    .thoughts-toolbar {
+        flex-direction: column;
+        align-items: stretch;
+    }
+    .thoughts-controls {
+        flex-direction: column;
+        gap: 8px;
+    }
+    .thoughts-search-input {
+        width: 100%;
+    }
+    .thoughts-sort-select {
+        width: 100%;
+    }
     .shelf-search {
         width: 140px;
     }