feat: add admin/internal database API with CRUD, read-only query, and natural-language SQL endpoints

Add a new `/dbapi` router package providing a generic database API over `dataset`, restricted to admin sessions, admin API keys, and the internal gateway key. Includes:

- `tables.py`: list all tables and inspect table schemas
- `crud.py`: full CRUD operations (GET, POST, PATCH, DELETE) with soft-delete awareness, born-live inserts, `?include_deleted`, `.../restore`, and `?hard=true` purge
- `query.py`: validated read-only SELECT execution via sqlglot parsing, classification, and EXPLAIN dry-run; async query jobs with WebSocket streaming via `DbApiJobService`
- `nl.py`: natural-language-to-SQL conversion using the platform AI gateway with re-prompting until validation passes

Also register `DbApiJobService` and `PubSubService` in the service manager, add `DBAPI_DIR` to config data paths, and force cleartext `http://` connections to HTTP/1.1 in `curl_transport` to fix large request failures against uvicorn's HTTP/1.1-only internal gateway.

devplacepy/templates/gist_detail.html

@@ -51,6 +51,8 @@
             {% set _type = "gist" %}{% set _uid = gist['uid'] %}{% set _bookmarked = bookmarked %}{% include "_bookmark_button.html" %}
             {% if is_owner %}
             <button type="button" class="gist-star-btn" data-modal="edit-gist-modal"><span class="icon">&#x270F;&#xFE0F;</span>Edit</button>
+            {% endif %}
+            {% if is_owner or is_admin(user) %}
             <form method="POST" action="/gists/delete/{{ gist['slug'] or gist['uid'] }}" style="display:inline;">
                 <button type="submit" class="gist-star-btn" data-confirm="Delete this gist?"><span class="icon">&#x1F5D1;&#xFE0F;</span>Delete</button>
             </form>