Add the module navigation contract: manifest v9, module routes, return-to-origin

Stage 1 PR 7 (ADR 0063). A module becomes a first-class part of the Dashboard.

- Manifest v9 = v8 plus optional `navigation`: a Lucide icon from the curated
  MODULE_NAVIGATION_ICONS set, and up to 12 primary pages (stable id, safe
  label, kebab-case path relative to the module root; no traversal, schemes,
  queries, duplicates, or nesting). Validated before activation.
- Version 8 stays accepted beside version 9, each read strictly as itself
  (discriminated union); no released manifest is rewritten. The template
  moves to v9; the released Signage 0.1.5 manifest is a test fixture.
- Real module routes: /<id> is the landing view, /<id>/<page> a declared
  page, anything beneath a page a module-owned detail route; anything else
  is not-found and mounts nothing. api/assets/display are never pages.
- Sidebar: declared icons, pages nested under an open module, one
  aria-current, collapsed and drawer behaviour; v8 modules unchanged.
- module-ui-sdk: ModuleUiHostContext.navigation (location, subscribe,
  navigate, link, settings), refusing anything outside the module's routes;
  undefined on the display host. Mount ABI unchanged.
- Return-to-origin: one `?return=` carrier on Settings URLs, validated by
  parseReturnTarget and against running modules' declared routes; Settings
  Back returns to exactly the originating module page, across refreshes.

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

templates/module/ekklesia.module.json

@@ -1,5 +1,5 @@
 {
-  "manifestVersion": 8,
+  "manifestVersion": 9,
   "id": "example",
   "name": "Example Module",
   "description": "A minimal Ekklesia module template with backend behavior and optional primary and display UI.",
@@ -48,6 +48,21 @@
       "description": "Renders this module's record summary inside a host module's own screen."
     }
   ],
+  "navigation": {
+    "icon": "clipboard-list",
+    "pages": [
+      {
+        "id": "records",
+        "label": "Records",
+        "path": "records"
+      },
+      {
+        "id": "about",
+        "label": "About",
+        "path": "about"
+      }
+    ]
+  },
   "entrypoints": {
     "server": "./dist/server/index.js",
     "schema": "./dist/schema/index.js",