mobile-connector: merge pairing+devices into one self-service Mobile App page

The two admin-only console pages become a single "Mobile App" page
visible to every logged-in user: connection status (with the last
connection error for troubleshooting), the device list (admin sees all,
others only their own), a pairing dialog with the QR, and — admin-only —
a settings dialog hosting the plugin config, including a relay picker
(official grayed out, test, custom URL). The generic plugin-detail
config form defers to it via the new Plugin::config_in_detail_page flag.

Pairing is now self-service: any user opens a window and the device
auto-binds to them; revocation is admin-for-anyone, owner-for-self;
(re)binding to another user stays admin-only. Binding-managed plugins
(manages_own_access) now expose their non-admin pages to all users and
self-scope per caller (web_pages_for). The relay client records the
error that ends a WS session and clears it on reconnect.

web/components/plugin-detail.js

@@ -97,11 +97,14 @@ export class PluginDetailPage extends LightElement {
         return;
       }
       this._plugin = p;
-      // If the plugin ships its own admin page (an `admin_only` web-page), the
-      // generic config form defers to it — see `_renderConfig`.
+      // If the plugin ships its own page(s), the generic config form may defer
+      // to them — see `_renderConfig`. Prefer an `admin_only` console page;
+      // otherwise any page of this plugin will do (e.g. mobile-connector's
+      // Mobile App page, which hosts its own settings dialog).
       try {
         const pages = await jf('/api/plugins/pages');
-        this._customPage = (pages ?? []).find(pg => pg.plugin_id === this._id && pg.admin_only) ?? null;
+        const mine = (pages ?? []).filter(pg => pg.plugin_id === this._id);
+        this._customPage = mine.find(pg => pg.admin_only) ?? mine[0] ?? null;
       } catch { this._customPage = null; }
       // Keep whatever the admin has already typed across a reload triggered by a save.
       this._draft = { ...(p.config || {}), ...(this._draft || {}) };
@@ -276,11 +279,13 @@ export class PluginDetailPage extends LightElement {
   _renderConfig() {
     const p = this._plugin;
     const fields = schemaFields(p.config_schema);
+    // The plugin hosts its own config UI in one of its pages (e.g. the mobile
+    // connector's settings dialog): link out instead of duplicating the form.
+    if (p.config_in_detail_page === false) {
+      return this._customPage ? this._renderConfigLink() : nothing;
+    }
     // Defer to the plugin's own admin page only when there is no generic
-    // instance-config to show. A plugin like mobile-connector ships operational
-    // pages (pairing, devices) *alongside* a real `config_schema` (relay_url,
-    // …); those pages are complements — already reachable from the sidebar — not
-    // replacements, so the config form must still render.
+    // instance-config to show.
     if (fields.length === 0 && this._customPage) return this._renderConfigLink();
     const draft = this._draft || {};
     return html`