fix(directory): dedupe access/admin groups on repeated promotion; stop self-healing on every GET

Three independent copies of the same bug: routes/discovery.js's
POST /discovery/promote/:slug (the actual "Promote" button in the UI)
and services/discovery_reconciler.js's autoPromote path both called
ResourceGroup.create() directly with no existence check -- unlike
routes/api_directory_admin.js's own ensureResourceGroup, which already
carried a comment describing this exact "groups appear 3x" bug and
fixing it, just not everywhere it occurred. ResourceGroup has no DB
unique constraint on (resourceId, groupCn), so a resource promoted
more than once (retried UI click, or the same LXC discovered from
multiple Proxmox cluster nodes) silently accumulated duplicate
access/admin rows every time. Added ResourceGroup.ensure() (the
existing check-then-create pattern, now on the model) and switched all
three call sites to it. New regression test in tests/reconciler.test.js.

Also: GET /api/directory-admin/resources ran a full group-model
self-heal fan-out (ensureSiteGroups per site + provisionResourceGroups
per resource, each several sequential LDAP round-trips) unconditionally
on every single list -- confirmed via code read as the actual
bottleneck once a directory has more than a handful of resources, not
data volume. Moved healing to where resources actually change instead
(POST/PUT /resources, POST /discovery/promote/:slug -- PUT had none at
all before this), and added POST /resources/heal-groups as an explicit
on-demand equivalent for backfilling a directory seeded before this
change.

nodejs/package.json

@@ -11,7 +11,7 @@
   "scripts": {
     "start": "node ./bin/www",
     "dev": "npx nodemon --ignore public/ ./bin/www",
-    "test": "NODE_ENV=test jest tests/groups.test.js tests/subtypes.test.js tests/site_join.test.js tests/site_config.test.js tests/site_replicate.test.js tests/proxy_client.test.js --forceExit"
+    "test": "NODE_ENV=test jest tests/groups.test.js tests/subtypes.test.js tests/site_join.test.js tests/site_config.test.js tests/site_replicate.test.js tests/proxy_client.test.js tests/reconciler.test.js --forceExit"
   },
   "jest": {
     "testEnvironment": "node",