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>

shopdb/__init__.py

@@ -152,11 +152,12 @@ def register_blueprints(app: Flask):
 def register_cli_commands(app: Flask):
     """Register Flask CLI commands."""
     from .plugins.cli import plugin_cli
-    from .cli import db_cli, seed_cli
+    from .cli import db_cli, seed_cli, relationships_cli
 
     app.cli.add_command(plugin_cli)
     app.cli.add_command(db_cli)
     app.cli.add_command(seed_cli)
+    app.cli.add_command(relationships_cli)
 
 
 def register_error_handlers(app: Flask):