Remove unused htmx/json-enc vendor libs; fix missing htm.js symlink

- Remove vendor/htmx-2.0.4.min.js and vendor/json-enc-2.0.0.js (unused)
- Remove webui/static/htmx.min.js and webui/static/json-enc.js symlinks
- Add webui/static/vendor/htm.js symlink pointing to project root
  vendor/htm.js, fixing the module script MIME type error caused by
  hoover/html.js importing from a non-existent path

webui/static/htmx.min.js

@@ -1 +0,0 @@
-../../vendor/htmx-2.0.4.min.js

webui/static/json-enc.js

@@ -1 +0,0 @@
-../../vendor/json-enc-2.0.0.js

webui/static/vendor/htm.js

@@ -0,0 +1 @@
+../../../vendor/htm.js