feat: list upcoming events with a create button

The list page now parses the calendar feed and renders each upcoming
event (title, date, place) in chronological order, with a button that
hands the event over to the town hall form.

Sorting, date formatting and the café fallback live in a pure
presentation module rather than in liste.js, which touches the DOM and
cannot be imported under bun test. The seam to the sibling task's
content script lives in transfert.js: a single storage slot, since a
content script running on the town hall site has no way to learn a uid.
The deposit is awaited before opening the tab, otherwise the content
script could read before the write lands.

Test timezone is pinned to Europe/Paris: date formatting is the core
logic here and would otherwise pass only on machines set to Paris.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -4,6 +4,6 @@
   "type": "module",
   "description": "Outillage de dev (Bun) pour l'extension. L'extension elle-même est du JS vanilla sans build.",
   "scripts": {
-    "test": "bun test"
+    "test": "TZ=Europe/Paris bun test"
   }
 }