feat: Notion-style Library page — complete redesign

Complete rewrite of /library page to match Notion's Library design:

1. Table view with columns: Page name (with icon), Created by (avatar),
   Source, Last edited time, Last visited time
2. Hover effects showing drag handle (6 dots), checkbox, OPEN button
3. Side peek panel: opens on right, shows page content preview,
   close button, favorite toggle, copy link, more menu
4. Multi-selection: checkbox per row, select-all header, 'X selected' bar
   with Delete and '...' menu
5. ... menu: Remove from Recents, Copy links to all, Move to, Move to Trash
6. Inline rename: double-click title → edit field
7. 6 tabs: Recents, Favorites, Shared, Published, Private, Workspace
8. Tree expand/collapse for nested pages (has_children support)
9. + Add new row at bottom
10. Search bar toggleable

API additions:
- library.py: enhanced _build_item with icon, source_label, author
- dashboard.py: new /api/pages/{id}/content, /rename, /trash endpoints
- All 133 tests pass

app/routers/dashboard.py

@@ -1844,3 +1844,51 @@ def _render_blocks_public(blocks: list) -> str:
         else:
             html_parts.append(f'<p style="margin:4px 0;line-height:1.7;">{c}</p>')
     return "\n".join(html_parts)
+
+
+# ═══════════ Library page actions API ═══════════
+
+@router.get("/api/pages/{page_id:int}/content")
+async def api_page_content(page_id: int):
+    """Get page content for side peek preview."""
+    with get_conn() as conn:
+        row = conn.execute(
+            "SELECT title, content, content_format FROM pages WHERE id=? AND deleted_at IS NULL",
+            (page_id,),
+        ).fetchone()
+        if not row:
+            return JSONResponse({"error": "Not found"}, status_code=404)
+    return {
+        "title": row["title"],
+        "content": row["content"],
+        "format": row["content_format"] or "blocks",
+    }
+
+
+@router.put("/api/pages/{page_id:int}/rename")
+async def api_rename_page(page_id: int, request: Request):
+    """Inline rename a page title."""
+    import json as _json
+    body = await request.json()
+    title = (body.get("title") or "").strip()
+    if not title:
+        return JSONResponse({"error": "Title required"}, status_code=400)
+    with get_conn() as conn:
+        conn.execute(
+            "UPDATE pages SET title=?, updated_at=CURRENT_TIMESTAMP WHERE id=? AND deleted_at IS NULL",
+            (title, page_id),
+        )
+        conn.commit()
+    return {"status": "ok", "title": title}
+
+
+@router.post("/api/pages/{page_id:int}/trash")
+async def api_trash_page(page_id: int):
+    """Soft-delete a page (move to trash)."""
+    with get_conn() as conn:
+        conn.execute(
+            "UPDATE pages SET parent_section='Trash', deleted_at=CURRENT_TIMESTAMP WHERE id=?",
+            (page_id,),
+        )
+        conn.commit()
+    return {"status": "ok"}