Add photo management for models and employees; fix stale detail navigation

Model photos: upload/replace/delete on /api/models/<id>/image (admin),
stored under instance/modelimages/ with a public serve route; thumbnail
plus Upload/Replace/Remove controls in the Models settings modal; the
URL field remains as a manual alternative.

Employee photos, mode-aware: self-hosted directory employees get
upload/replace/delete (photo-<sso> under instance/employeephotos/,
employees plugin migration 0002); external directory mode passes the
HR-supplied picture URL through read-only (writes 409). One resolver
feeds both consumers - the shopfloor recognition/recert kiosk cards and
the employee detail hero - in either mode.

Navigation fix: router-view is keyed on route path, so following a
relationship link between two assets of the same type (machine ->
dualpath machine) reloads the page instead of showing stale content;
query-only URL changes still avoid a remount.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

frontend/src/views/ShopfloorDashboard.vue

@@ -47,7 +47,7 @@
             <div class="recognition-photo-container">
               <img
                 v-if="rec.employeepicture"
-                :src="`/static/employees/${rec.employeepicture}`"
+                :src="rec.employeepicture"
                 :alt="rec.employeename"
                 class="recognition-photo"
                 @error="handlePhotoError"
@@ -91,7 +91,7 @@
           >
             <img
               v-if="rec.employeepicture"
-              :src="`/static/employees/${rec.employeepicture}`"
+              :src="rec.employeepicture"
               :alt="rec.employeename"
               class="recert-photo"
               @error="handlePhotoError"