Add fragment composition infrastructure for micro-frontend UI

New HTTP client (fragments.py) fetches HTML fragments from other apps
over the Docker network, with Redis caching and graceful degradation.
Jinja global `fragment()` available in all templates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infrastructure/jinja_setup.py

@@ -107,5 +107,14 @@ def setup_jinja(app: Quart) -> None:
     from shared.services.widget_registry import widgets as _widget_registry
     app.jinja_env.globals["widgets"] = _widget_registry
 
+    # fragment composition helper — fetch HTML from another app's fragment API
+    from shared.infrastructure.fragments import fetch_fragment_cached
+
+    async def _fragment(app_name: str, fragment_type: str, ttl: int = 30, **params) -> str:
+        p = params if params else None
+        return await fetch_fragment_cached(app_name, fragment_type, params=p, ttl=ttl)
+
+    app.jinja_env.globals["fragment"] = _fragment
+
     # register jinja filters
     register_filters(app)