fix(crawler): wait for page marker instead of fixed 1s sleep (0.36.2)

A chromium snapshot taken between the wrapper-render and row-render
phases let parse_chapter_list return Ok(vec![]) for a manga that
actually has chapters — the soft-drop branch in sync_manga_chapters
then flipped every existing chapter to dropped_at.

Add wait_for_selector to crawler::nav. navigate() now takes a CSS
marker matching the most-specific element the downstream parser will
look for (one of LIST_PAGE_MARKER / DETAIL_PAGE_CHAPTERS_MARKER /
DETAIL_PAGE_LAYOUT_MARKER). The wait is best-effort and capped by
SELECTOR_TIMEOUT (10s); a legitimately empty page can still pass
through because the parser's #chapter_table sentinel and the
universal broken-page body check stay in force.

Same pattern wired at the reader nav (a#pic_container) and probe
nav (#logo), replacing the implicit assumption that the post-load
JS had finished within 1 second.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.36.1",
+  "version": "0.36.2",
   "private": true,
   "type": "module",
   "scripts": {