fix: A10 — autoescape Jinja2 activé partout via un Environment partagé

- `app/templating.py` : `ENV = Environment(loader=FileSystemLoader("app/templates"), autoescape=select_autoescape(["html"]))`
- les 29 instantiations `Environment(loader=FileSystemLoader("app/templates"))` (9 routers) remplacées par `env = ENV` — plus aucune interpolation `{{ … }}` servie crue, les `|safe` redeviennent efficaces
- re-tri des `|safe` : `card_detail.html` corps d'issue et commentaires échappés (XSS stocké), placeholder de description sorti du ternaire, `sidebar_config` passé en dict + `|tojson` (échappement `</script>` en contexte script)
- `|safe` conservé sur `right_actions` (HTML fabriqué dans les templates, fiable)
- `ruff check app tests` OK · suite **1016/1016 verts**

app/routers/board.py

@@ -804,7 +804,7 @@ def _sidebar_data(request: Request, owner: str = "", repo: str = "") -> dict:
             "has_active_workspace": has_active_workspace,
             "app_version": _get_app_version(),
             "local_workspaces": _local_workspaces_for_user(user),
-            "sidebar_config": json.dumps(get_sidebar_config_sync(uid))}
+            "sidebar_config": get_sidebar_config_sync(uid)}
 
 
 def _extract_ai_keywords(owner: str, repo: str, labels: list[dict], body: str = ""):
@@ -908,8 +908,8 @@ def _apply_sorts(cards: list[dict], sorts: str) -> list[dict]:
 @router.get("/library", response_class=HTMLResponse)
 async def library_page(request: Request, owner: str = Query(default=""), repo: str = Query(default="")):
     """Library page avec onglets Recents, Favorites, Shared, Private — scopé au workspace."""
-    from jinja2 import Environment, FileSystemLoader
-    env = Environment(loader=FileSystemLoader("app/templates"))
+    from app.templating import ENV
+    env = ENV
     sidebar = _sidebar_data(request, owner, repo)
     # Load all pages for the workspace from DB
     ws_key = f"{owner}/{repo}" if owner and repo else ""
@@ -1084,8 +1084,8 @@ async def permanent_delete(request: Request, page_id: int):
 
 @router.get("/trash", response_class=HTMLResponse)
 async def trash_page(request: Request):
-    from jinja2 import Environment, FileSystemLoader
-    env = Environment(loader=FileSystemLoader("app/templates"))
+    from app.templating import ENV
+    env = ENV
     template = env.get_template("trash.html")
     return template.render(**_sidebar_data(request))
 
@@ -1213,8 +1213,8 @@ async def get_page_synced_refs(request: Request, page_id: int):
 
 @router.get("/{owner}/{repo}", response_class=HTMLResponse)
 async def board(request: Request, owner: str, repo: str, view: str = Query(default="")):
-    from jinja2 import Environment, FileSystemLoader
-    env = Environment(loader=FileSystemLoader("app/templates"))
+    from app.templating import ENV
+    env = ENV
     sidebar = _sidebar_data(request, owner, repo)
     template = env.get_template("board.html")
     return template.render(request=request, owner=owner, repo=repo, groups=[],
@@ -1240,8 +1240,8 @@ async def board_view(
         logger.error("Board view error: %s", e)
         cards = []
 
-    from jinja2 import Environment, FileSystemLoader
-    env = Environment(loader=FileSystemLoader("app/templates"))
+    from app.templating import ENV
+    env = ENV
 
     # Dynamic groups from Gitea labels (fallback to hardcoded)
     group_names = ["Design", "Engineering", "No Team"]
@@ -2047,8 +2047,8 @@ async def view_page(request: Request, page_id: int):
     """Render a page as HTML, or a file viewer for uploaded files.
     ?embed=1 — minimal mode for side peek (editor only, no header)."""
     embed = request.query_params.get("embed") == "1"
-    from jinja2 import Environment, FileSystemLoader
-    env = Environment(loader=FileSystemLoader("app/templates"))
+    from app.templating import ENV
+    env = ENV
     # v6.0.0: granular page permissions — hide restricted pages (404).
     user_hdr = SessionManager.decode_session(request.cookies.get("flowdeck_session", ""))
     if user_hdr and user_hdr.get("id") and not PermissionManager(user_hdr["id"]).can_view_page(page_id):