feat(telegram): candidate list/delete/clear commands

私聊新增 /candidate [页码]（待决策列表）、/candi_del（标题按钮逐条删除，删后原地重建键盘、可翻页连续删）、/candi_clear（全部/待决策/取消）。重构 handle_callback 为前缀分派（cdel/cpage/cclr，保留 add/ign/blk/fav）；repository 加 list_pending_candidates/delete_all_candidates；LibraryService 加 pending_candidates/delete_candidate/clear_candidates 并刷看板缓存。

reaction_board/notify/telegram.py

@@ -89,10 +89,85 @@ def format_manual_reply(manual_result: Any) -> str:
 
 HELP_TEXT = (
     "发送 B 站视频链接、BV 号或 av 号即可手动入库并开始追踪。\n"
-    "例如：https://www.bilibili.com/video/BV1x8x166EzY 或 BV1x8x166EzY"
+    "例如：https://www.bilibili.com/video/BV1x8x166EzY 或 BV1x8x166EzY\n"
+    "\n"
+    "候选管理命令：\n"
+    "/candidate [页码]  查看待决策候选列表\n"
+    "/candi_del  用按钮删除指定候选\n"
+    "/candi_clear  清空候选库"
 )
 
 
+CANDIDATE_PAGE_SIZE = 10
+TITLE_BUTTON_LIMIT = 28
+CANDIDATE_DELETE_HEADER = "待决策候选：点击标题删除对应候选。"
+
+
+def truncate_title(title: object, limit: int = TITLE_BUTTON_LIMIT) -> str:
+    """把标题截断到适合作为按钮文案的长度（超出补 …）。"""
+    text = str(title or "").strip() or "(无标题)"
+    if len(text) <= limit:
+        return text
+    return text[: max(1, limit - 1)] + "…"
+
+
+def _page_bounds(total: int, page: int, page_size: int) -> tuple[int, int, int]:
+    total_pages = max(1, (total + page_size - 1) // page_size)
+    try:
+        page = int(page)
+    except (TypeError, ValueError):
+        page = 1
+    page = min(max(1, page), total_pages)
+    return page, total_pages, (page - 1) * page_size
+
+
+def format_candidate_list(
+    items: Sequence[Mapping[str, Any]],
+    page: int = 1,
+    page_size: int = CANDIDATE_PAGE_SIZE,
+) -> str:
+    """待决策候选的纯文本列表（每页 ``page_size`` 条）。"""
+    total = len(items)
+    if total == 0:
+        return "暂无待决策候选。"
+    page, total_pages, start = _page_bounds(total, page, page_size)
+    lines = [f"待决策候选 共 {total} 条 · 第 {page}/{total_pages} 页"]
+    for item in items[start:start + page_size]:
+        title = html.escape(str(item.get("title") or "(无标题)"))
+        lines.append(f"· {title}")
+    return "\n".join(lines)
+
+
+def candidate_delete_keyboard(
+    items: Sequence[Mapping[str, Any]],
+    page: int = 1,
+    page_size: int = CANDIDATE_PAGE_SIZE,
+) -> dict[str, Any]:
+    """每页每条标题一个按钮（``cdel:<page>:<aid>``）+ 翻页按钮。"""
+    total = len(items)
+    page, total_pages, start = _page_bounds(total, page, page_size)
+    rows: list[list[Mapping[str, Any]]] = []
+    for item in items[start:start + page_size]:
+        rows.append([{
+            "text": truncate_title(item.get("title")),
+            "callback_data": f"cdel:{page}:{item.get('aid')}",
+        }])
+    if total_pages > 1:
+        rows.append([
+            {"text": "上一页", "callback_data": f"cpage:del:{page - 1}"},
+            {"text": "下一页", "callback_data": f"cpage:del:{page + 1}"},
+        ])
+    return {"inline_keyboard": rows}
+
+
+def clear_candidates_keyboard() -> dict[str, Any]:
+    return {"inline_keyboard": [[
+        {"text": "全部", "callback_data": "cclr:all"},
+        {"text": "待决策", "callback_data": "cclr:pending"},
+        {"text": "取消", "callback_data": "cclr:cancel"},
+    ]]}
+
+
 def format_candidate(candidate: Mapping[str, Any]) -> str:
     title = html.escape(str(candidate.get("title") or "(无标题)"))
     up_name = html.escape(str(candidate.get("up_name") or "未知UP"))