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>

transfert.test.ts

@@ -0,0 +1,86 @@
+import { describe, expect, test } from "bun:test";
+import {
+  CLE_EVENEMENT_EN_ATTENTE,
+  deposerEvenement,
+  serialiserPourFormulaire,
+} from "./extension/transfert.js";
+
+function evenement(surcharges: Record<string, unknown> = {}) {
+  return {
+    uid: "uid-1",
+    titre: "Atelier",
+    description: "Venez nombreux",
+    lieu: "Salle des fêtes",
+    debut: new Date("2026-07-10T16:00:00Z"),
+    fin: new Date("2026-07-10T18:00:00Z"),
+    categories: ["soumis"],
+    journeeEntiere: false,
+    ...surcharges,
+  };
+}
+
+// Storage factice (Chicago) : capture ce qui est écrit, pas de mock lourd.
+function storageFactice() {
+  const ecrit: Record<string, unknown> = {};
+  return {
+    ecrit,
+    set: async (objet: Record<string, unknown>) => Object.assign(ecrit, objet),
+  };
+}
+
+describe("serialiserPourFormulaire", () => {
+  test("debut et fin deviennent des chaînes ISO", () => {
+    const payload = serialiserPourFormulaire(evenement());
+
+    expect(payload.debut).toBe("2026-07-10T16:00:00.000Z");
+    expect(payload.fin).toBe("2026-07-10T18:00:00.000Z");
+  });
+
+  test("un lieu vide reste vide (pas de défaut café — D4)", () => {
+    const payload = serialiserPourFormulaire(evenement({ lieu: "" }));
+
+    expect(payload.lieu).toBe("");
+  });
+
+  test("porte tous les champs du contrat Event", () => {
+    const payload = serialiserPourFormulaire(evenement());
+
+    expect(payload).toEqual({
+      uid: "uid-1",
+      titre: "Atelier",
+      description: "Venez nombreux",
+      lieu: "Salle des fêtes",
+      debut: "2026-07-10T16:00:00.000Z",
+      fin: "2026-07-10T18:00:00.000Z",
+      categories: ["soumis"],
+      journeeEntiere: false,
+    });
+  });
+
+  test("aller-retour : le content script peut réhydrater debut", () => {
+    const ev = evenement();
+    const payload = serialiserPourFormulaire(ev);
+
+    expect(new Date(payload.debut).getTime()).toBe(ev.debut.getTime());
+  });
+});
+
+describe("deposerEvenement", () => {
+  test("écrit sous la clé evenement-en-attente", async () => {
+    const storage = storageFactice();
+
+    await deposerEvenement(storage, evenement());
+
+    expect(storage.ecrit[CLE_EVENEMENT_EN_ATTENTE]).toMatchObject({ uid: "uid-1" });
+  });
+
+  test("un second dépôt écrase le premier (slot unique — D2)", async () => {
+    const storage = storageFactice();
+
+    await deposerEvenement(storage, evenement({ uid: "premier" }));
+    await deposerEvenement(storage, evenement({ uid: "second" }));
+
+    expect(Object.keys(storage.ecrit)).toEqual([CLE_EVENEMENT_EN_ATTENTE]);
+    expect(storage.ecrit[CLE_EVENEMENT_EN_ATTENTE]).toMatchObject({ uid: "second" });
+  });
+});