fix: sidebar vide sur /workspaces — pas de contexte workspace actif

_sidebar_data() prend un nouveau parametre include_workspace (default True).
La page /workspaces passe include_workspace=False pour que la sidebar
n'affiche ni le nom du workspace actif, ni ses pages/folders.

app/routers/dashboard.py

@@ -31,7 +31,7 @@ def _get_user_or_redirect(request: Request):
     return user
 
 
-def _sidebar_data(request: Request, repos: list[dict]) -> dict:
+def _sidebar_data(request: Request, repos: list[dict], include_workspace: bool = True) -> dict:
     user = SessionManager.decode_session(request.cookies.get("flowdeck_session", ""))
     ws = user.get("login", "Bruno") if user else "Bruno"
     initial = ws[0].upper() if ws else "B"
@@ -64,7 +64,8 @@ def _sidebar_data(request: Request, repos: list[dict]) -> dict:
             "children": [],
         })
 
-    # Active workspace from cookie
+    # Active workspace from cookie (skip on pages like /workspaces where no
+    # workspace context should be shown)
     from app.routers.board import _load_workspace_pages
     ws_cookie = request.cookies.get("flowdeck_workspace", "")
     active_ws_name = "Workspace"
@@ -73,7 +74,7 @@ def _sidebar_data(request: Request, repos: list[dict]) -> dict:
     gitea_owner = ""
     gitea_repo = ""
 
-    if ws_cookie and ws_cookie.startswith("gitea:"):
+    if include_workspace and ws_cookie and ws_cookie.startswith("gitea:"):
         # Gitea workspace: set owner/repo for client-side tree loading
         parts = ws_cookie.split(":", 2)
         if len(parts) >= 3:
@@ -82,7 +83,7 @@ def _sidebar_data(request: Request, repos: list[dict]) -> dict:
             active_ws_name = f"{gitea_owner}/{gitea_repo}"
             gitea_workspace = True
             workspace_pages = []  # loaded client-side
-    elif ws_cookie and user:
+    elif include_workspace and ws_cookie and user:
         try:
             wsi = int(ws_cookie)
             with get_conn() as conn:
@@ -1105,7 +1106,7 @@ async def workspaces_page(request: Request):
     """Workspaces list page."""
     from jinja2 import Environment, FileSystemLoader
     env = Environment(loader=FileSystemLoader("app/templates"))
-    sidebar = _sidebar_data(request, [])
+    sidebar = _sidebar_data(request, [], include_workspace=False)
     user = SessionManager.decode_session(request.cookies.get("flowdeck_session", ""))
     if not user:
         return RedirectResponse("/auth/login?provider=local", status_code=302)