feat(directory): real mesh-gateway count on the Multi-Site modal; docs links

"Theta Gateways: N active gateways" was counting this app's own
unrelated WireGuard roaming-client/exit-node Resources
(metadata.subType === 'wireguard') -- a completely different subsystem
from the gateway-to-gateway mesh the modal is actually about, and it
never queried jump-host's mesh registry at all (so it couldn't show
the local self-entry either, since there was nothing mesh-related
being counted in the first place).

Added utils/jump_client.js (same pattern as utils/proxy_client.js:
reuses jump-host's existing self-service jmp_ API token system rather
than inventing a new credential) to query jump-host's real
GET /api/mesh/gateways. Reports a null count (not misleading 0) when
the integration isn't configured/reachable, surfaced distinctly in the
UI. Also added help links to the published multi-site/mesh docs on the
modal.

Includes docs links + count only -- this session also discovered that
utils/proxy_client.js's PROXY_INTERNAL_URL, and now JUMP_INTERNAL_URL,
were never actually wired into theta-suite's docker-compose.yml, so
both service-to-service integrations were unreachable in every real
deployment despite existing in code (fixed in theta-suite separately).

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/jump_client.test.js --forceExit"
   },
   "jest": {
     "testEnvironment": "node",