dotAI portlet: design + QA follow-ups from the Dojo to Angular migration

[fmontes]

Description

Design and QA review of the new Angular dotAI portlet (#37417) turned up seven follow-ups — five UI/copy corrections and two bugs in the Embeddings tab. Grouping them into one issue since they all land in the same portlet and are best fixed and QA'd together.

1. Empty states don't match the platform. The portlet rolled its own empty state instead of the dot-empty-container every other portlet uses. Replace it everywhere.
2. Fields and Velocity template need real descriptions. The Velocity template has no hint and no placeholder at all, and the Fields hint is wrong — it says "leave empty to embed the whole contentlet" when dotCMS actually picks a subset of fields. The two are also alternatives, not complements: a Velocity template overrides Fields entirely. None of that is visible in the dialog. Needs a hint on both plus an example placeholder on the template.
3. Remove "View provider config". The button and its JSON dialog in Config Values aren't needed.
4. "Rebuild DB" is red. Should be a regular outlined button — the destructive step is already the confirm dialog.
5. The Config Values host line is unclear. It reads demo.dotcms.com (falls back to system host), which doesn't say what it means and isn't translatable.
6. Build warnings appear behind the modal. Submitting the Build an index dialog closes it, then shows the outcome — including Lucene query errors — in the tab behind it. The user loses what they typed and has to start over. Keep the modal open and show it there.
7. A new index doesn't appear in the table. After building, the row only shows up after a manual page reload.

Acceptance Criteria

• Every dotAI empty state uses dot-empty-container from @dotcms/ui and matches the empty states in other portlets
• Velocity template has a hint and an example placeholder; the Fields hint is corrected, and it's clear a template overrides Fields
• The View provider config button and dialog are gone
• Rebuild DB renders as a regular outlined button
• The Config Values host line reads clearly and is translatable
• Building an index keeps the modal open and shows success, "nothing matched", and query errors inline, with the typed values preserved; it closes only on success
• A new index appears in the Embeddings table as Building right after submit and flips to Ready on its own, with no page reload

Additional Context

Follow-up to #37417 (Dojo to Angular: dotAI Portlet), implemented in #37423. Feedback from Jorge Conde (9/11) and melissa.rojas (9/10).

Items 6 and 7 are defects; 1–5 are UI/copy. Items 2 and 5 touch the backend; the rest are frontend-only.

[github-actions]

PRs linked to this issue

• fix(dotai): design and QA follow-ups from the Angular migration (#37538) by @fmontes