feat(reader): in-book search for reflowable formats

Wires foliate's search engine into the new drawer system:

- 🔍 topbar button (reflowable-only; PDF/comic sections have no
  searchable text documents) and the '/' keyboard shortcut open a
  Search drawer: query input (Enter to run), live progress while
  scanning (per-section percent), match count, and results grouped
  by section with TOC labels.
- Each result shows pre/match/post excerpt rendered as three text
  nodes (no x-html — book content never enters the DOM as markup);
  the match is styled with a translucent <mark>. Clicking jumps to
  the hit's CFI and closes the drawer.
- Hits are drawn on the page through foliate's overlayer (outline
  style) and persist across page turns — the engine re-applies
  search results when a section's overlay is created. Clearing the
  query removes the outlines.
- A generation counter discards results and progress from superseded
  searches (rapid re-query), and starting a new search clears the
  previous one server-side via view.clearSearch().
- Search integrates with the drawer system: scrim, Esc-to-close,
  one-drawer-at-a-time, / focuses the input via .

web/static/input.css

@@ -991,6 +991,40 @@
     gap: 0.25rem;
   }
 
+  /* In-book search */
+  .reader-search-bar {
+    display: flex;
+    align-items: center;
+    gap: 0.375rem;
+    padding: 0.625rem 1rem;
+    border-bottom: 1px solid var(--border);
+    flex-shrink: 0;
+  }
+  .reader-search-status {
+    padding: 0.375rem 1rem;
+    font-size: 0.75rem;
+    color: var(--text-secondary);
+    border-bottom: 1px solid color-mix(in srgb, var(--border) 50%, transparent);
+    flex-shrink: 0;
+    min-height: 1.75rem;
+  }
+  .search-result {
+    display: block;
+    padding: 0.375rem 0.5rem;
+    border-radius: 0.375rem;
+    font-size: 0.8125rem;
+    line-height: 1.35;
+  }
+  .search-result:hover {
+    background-color: color-mix(in srgb, currentColor 9%, transparent);
+  }
+  .search-result mark {
+    background-color: rgba(255, 213, 79, 0.4);
+    color: inherit;
+    border-radius: 2px;
+    padding: 0 1px;
+  }
+
   /* ---------- Series stacked covers ---------- */
   .stacked-covers {
     position: relative;