feat(shell): give every Dashboard page a real URL

The Dashboard had one address. The API served the page only at `/`, both
reference proxies forwarded only `/`, and the open module lived in React
state, so a refresh went back to the first module, nothing could be
bookmarked, and Back left the Dashboard (DESIGN.md §2.7).

ADR 0057 makes the address bar the source of truth:

- `/` is a host-owned Overview, now the landing page; `/modules/<id>`
  mounts that module. An id the server's navigation does not list shows
  "This page isn't available" and loads nothing; any other Dashboard
  address is a host-owned "Page not found".
- `/modules`, `/settings`, and `/account` are reserved whole, from one
  list (`@ekklesia/shell/dashboard-routes`) that the shell's router and
  the API's page routes both read. The API serves the same frozen page,
  ETag, and security headers anywhere inside them; look-alikes and other
  methods stay the sanitized 404.
- A small host-owned history replaces the selected-module state, built in
  the entry point so it stays the only file touching `window`. Navigation
  items are real links; modified clicks are left to the browser. Focus
  moves to the page after an in-place change, and the tab is named after
  the page.
- Sign-in still happens in place with no return value (ADR 0034), so a
  deep link opens its own page after sign-in.
- Both reference Caddyfiles forward the new paths; the deploy smoke now
  reloads a module's address through the real proxy and requires it to
  mount again.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

surfaces/shell/tests/auth-recovery.test.tsx

@@ -3,6 +3,7 @@ import { createRoot, type Root } from "react-dom/client";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { consumeAuthLanding, type HostAuthLanding, readAuthLanding } from "../src/auth-protocol.js";
 import { HostApp } from "../src/browser/HostApp.js";
+import { createMemoryHostHistory } from "../src/browser/host-history.js";
 import type { EkklesiaHostConfig } from "../src/host-protocol.js";
 
 /**
@@ -94,7 +95,13 @@ function platform(stub: AuthStub = {}): Platform {
 
 async function render(config: EkklesiaHostConfig, authLanding?: HostAuthLanding): Promise<void> {
   await act(async () => {
-    root.render(<HostApp config={config} {...(authLanding ? { authLanding } : {})} />);
+    root.render(
+      <HostApp
+        config={config}
+        history={createMemoryHostHistory("/")}
+        {...(authLanding ? { authLanding } : {})}
+      />,
+    );
   });
 }