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]>

README.md

@@ -822,7 +822,8 @@ hosting are deployment work, not guarantees added by this pass. Display device i
 public Website remain separate future designs.
 
 **Still not the finished Dashboard.** There is no navigation editor or drag and drop, no nested
-folders, no icons or colors, no Dashboard Home or widgets, no design system, no client-side routing,
+folders, no icons or colors, no Dashboard Home or widgets, no design system, no client-side routing
+(since added; see the Stage 1 paragraph below),
 and no module-management, settings, or storage UI — module enablement and configuration are an API and
 a CLI, not a screen, and object storage is deployment configuration. A production CSP and
 deployment for the built shells, general sidecar asset publication, React runtime sharing, the
@@ -905,6 +906,17 @@ the module's responsibility and do not exist yet.**
 Ekklesia Lite, a theme editor, a module store or installer, a standalone host, and every feature
 module — Signage included — still do not exist, and nothing in Phase 8 claims otherwise.
 
+Stage 1 begins with **real Dashboard URLs**
+([ADR 0057](docs/architecture/decisions/0057-dashboard-urls-are-host-owned-routes.md)). The
+Dashboard opens on an **Overview** at `/`, and each module's page has its own address,
+`/modules/<module-id>`, so a refresh, a bookmark, and a shared link land on the page that was open
+and Back and Forward walk the Dashboard's own pages. The API serves the same Dashboard page at `/` and
+throughout the reserved `/modules`, `/settings`, and `/account` namespaces, and both reference proxies
+forward them. A module that is not in the server's navigation — disabled, removed, or with no UI —
+shows a host-owned *This page isn't available* rather than loading anything. A module's own
+sub-pages, Settings and Account pages, the sidebar redesign, and returning to the workflow a Settings
+link came from are later Stage 1 work.
+
 ## Quick start
 
 Prerequisites: Node.js 24 LTS, pnpm 11.12, and Docker with Compose.