fix(web): keep the dedicated-environment link on a custom Cloud banner (#2760)

* fix(web): keep the dedicated-environment link on a custom Cloud banner

The Cloud banner can carry per-language copy, but the custom-copy branch
rendered that text alone: everything else in the banner swaps the built-in
message for an override so the operator can say what is actually happening,
and doing so silently dropped the link to the dedicated environment -- the only
destination that turns a warning into an upgrade.

Render the dedicated link after the override when show_links is on, using new
cta_dedicated copy in every locale so the second half of the sentence reads as
a call to action rather than repeating the environment name.

* test(web): expect the new banner CTA copy in every locale

web/tests/unit/cloud-banner.test.mjs

@@ -75,6 +75,7 @@ test('every locale carries the cloud_banner copy', () => {
   const expectedKeys = [
     'message',
     'dedicated_link',
+    'cta_dedicated',
     'or',
     'self_hosted_link',
     'period',