fix(frontend,application,backend,web-server,infrastructure): le set de couleurs projet s'applique à tous les projets — #316 (QA verte)

Cause: update_project_settings remplaçait tout ProjectSettings avec la
seule couleur fournie — champ absent et null indistinguables — et des
réponses de chargement/sauvegarde obsolètes d'un projet précédent
pouvaient réafficher/écraser la couleur lors d'un changement de projet
rapide, d'où l'impression que la couleur ne prenait pas sur tous les
projets.

- DTO tri-état (absent = inchangé, null = défaut produit) avec
  Deserialize manuel et use case de mise à jour partielle du champ
  theme_color; commandes Tauri et web-server alignées sur le même
  contrat.
- Garde-fous de course frontend: séquences load/save + révision thème
  par projet (pub/sub onProjectThemeChanged) dans ProjectSettingsPanel,
  garde de révision de focus dans ViewWindow.
- Tests: infrastructure settings, contrats web-server (inchangé/reset),
  ProjectSettingsPanel, ViewWindow, projects.

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

frontend/src/features/projects/ProjectSettingsPanel.test.tsx

@@ -4,7 +4,19 @@ import { describe, expect, it, vi } from "vitest";
 import { createMockGateways } from "@/adapters/mock";
 import { DIProvider } from "@/app/di";
 import { ProjectSettingsPanel, PROJECT_THEME_CHANGED_EVENT } from "./ProjectSettingsPanel";
-import { accessibleProjectAccent, validThemeColor } from "./projectTheme";
+import {
+  accessibleProjectAccent,
+  publishProjectThemeChanged,
+  validThemeColor,
+} from "./projectTheme";
+
+function deferred<T>() {
+  let resolve!: (value: T) => void;
+  const promise = new Promise<T>((done) => {
+    resolve = done;
+  });
+  return { promise, resolve };
+}
 
 describe("ProjectSettingsPanel", () => {
   it("persists a project colour, emits the scoped refresh, and resets to fallback", async () => {
@@ -55,6 +67,83 @@ describe("ProjectSettingsPanel", () => {
     );
   });
 
+  it("keeps sibling settings surfaces in sync without persisting the blue fallback", async () => {
+    const gateways = createMockGateways();
+    const project = await gateways.project.createProject("Alpha", "/alpha");
+    const update = vi.spyOn(gateways.project, "updateProjectSettings");
+    render(
+      <DIProvider gateways={gateways}>
+        <ProjectSettingsPanel projectId={project.id} />
+        <ProjectSettingsPanel projectId={project.id} />
+      </DIProvider>,
+    );
+
+    const pickers = (await screen.findAllByLabelText(
+      "Couleur du projet",
+    )) as HTMLInputElement[];
+    await waitFor(() =>
+      expect(pickers.every((picker) => !picker.disabled)).toBe(true),
+    );
+    expect(pickers.map((picker) => picker.value)).toEqual(["#4c8dff", "#4c8dff"]);
+    expect(update).not.toHaveBeenCalled();
+
+    fireEvent.change(pickers[0], { target: { value: "#aa3366" } });
+    await waitFor(() => expect(pickers[1].value).toBe("#aa3366"));
+  });
+
+  it("does not let a delayed read replace a newer cross-window colour", async () => {
+    const gateways = createMockGateways();
+    const project = await gateways.project.createProject("Alpha", "/alpha");
+    const pendingRead = deferred<{ themeColor: string | null }>();
+    vi.spyOn(gateways.project, "readProjectSettings").mockReturnValue(
+      pendingRead.promise,
+    );
+    render(
+      <DIProvider gateways={gateways}>
+        <ProjectSettingsPanel projectId={project.id} />
+      </DIProvider>,
+    );
+
+    publishProjectThemeChanged({ projectId: project.id, themeColor: "#22AA66" });
+    pendingRead.resolve({ themeColor: "#AA3366" });
+
+    await waitFor(() =>
+      expect((screen.getByLabelText("Couleur du projet") as HTMLInputElement).value).toBe(
+        "#22aa66",
+      ),
+    );
+  });
+
+  it("does not apply a delayed save response to the newly edited project", async () => {
+    const gateways = createMockGateways();
+    const alpha = await gateways.project.createProject("Alpha", "/alpha");
+    const beta = await gateways.project.createProject("Beta", "/beta");
+    await gateways.project.updateProjectSettings(beta.id, { themeColor: "#22AA66" });
+    const pendingSave = deferred<{ themeColor: string | null }>();
+    vi.spyOn(gateways.project, "updateProjectSettings").mockImplementation(
+      async (projectId, settings) =>
+        projectId === alpha.id ? pendingSave.promise : settings,
+    );
+    const view = render(
+      <DIProvider gateways={gateways}>
+        <ProjectSettingsPanel projectId={alpha.id} />
+      </DIProvider>,
+    );
+
+    const picker = (await screen.findByLabelText("Couleur du projet")) as HTMLInputElement;
+    await waitFor(() => expect(picker.disabled).toBe(false));
+    fireEvent.change(picker, { target: { value: "#aa3366" } });
+    view.rerender(
+      <DIProvider gateways={gateways}>
+        <ProjectSettingsPanel projectId={beta.id} />
+      </DIProvider>,
+    );
+    await waitFor(() => expect(picker.value).toBe("#22aa66"));
+
+    pendingSave.resolve({ themeColor: "#AA3366" });
+    await waitFor(() => expect(picker.value).toBe("#22aa66"));
+  });
+
   it("keeps strict colours and raises dark accents to readable contrast", () => {
     expect(validThemeColor("#12abEF")).toBe("#12ABEF");
     expect(validThemeColor("red")).toBeNull();