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/my_tasks.py

@@ -6,10 +6,10 @@ import logging
 
 from fastapi import APIRouter, Request
 from fastapi.responses import HTMLResponse
-from jinja2 import Environment, FileSystemLoader
 
 from app.auth.session import SessionManager
 from app.db import get_conn
+from app.templating import ENV
 
 logger = logging.getLogger(__name__)
 router = APIRouter(tags=["my-tasks"], prefix="/my-tasks")
@@ -102,7 +102,7 @@ async def my_tasks_dashboard(request: Request, view: str = "all", days: int = 7)
 </div>"""
 
     from app.routers.dashboard import _sidebar_data
-    env = Environment(loader=FileSystemLoader("app/templates"))
+    env = ENV
     sidebar = _sidebar_data(request, [])
     block_tpl = env.from_string(
         '{% extends "base.html" %}{% block content %}{{ content_html|safe }}{% endblock %}'