fix: sidebar Favorites + Shared, Library page with tabs, CSRF fix

- Section Favorites ajoutée dans le sidebar (⭐)
- Section Shared ajoutée (👥)
- Section Library remplacée par bouton 📚 qui ouvre /library
- Page /library avec onglets: Recents | Favorites | Shared | Private
- CSRF token injecté dans les appels fetch (newPage, newSubPage)
- Bouton + sur éléments sidebar corrigé (POST /board/api/pages avec X-CSRF-Token)
- Bouton 📚 sur sections ouvre /library
- sidebar_data inclut favorite_pages=[]

app/routers/dashboard.py

@@ -48,10 +48,25 @@ def _sidebar_data(request: Request, repos: list[dict]) -> dict:
         "current_page": "Dashboard", "last_edited": "now",
         "recent_pages": recent_pages,
         "private_pages": [p for p in recent_pages if p["id"].startswith("page/")],
+        "favorite_pages": [],
         "user": user,
     }
 
 
+@router.get("/library", response_class=HTMLResponse)
+async def library_page(request: Request):
+    """Library page avec onglets Recents, Favorites, Shared, Private."""
+    from jinja2 import Environment, FileSystemLoader
+    env = Environment(loader=FileSystemLoader("app/templates"))
+    sidebar = _sidebar_data(request, [])
+    for p in sidebar["recent_pages"]:
+        p["last_edited"] = "now"
+    for p in sidebar["private_pages"]:
+        p["last_edited"] = "now"
+    template = env.get_template("library.html")
+    return template.render(**sidebar)
+
+
 @router.get("/", response_class=HTMLResponse)
 async def dashboard(
     request: Request,