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/curl_transport.py

@@ -45,6 +45,12 @@ HTTP_VERSION_LABELS: dict[int, bytes] = {
 }
 
 
+def http_version_for(url: httpx.URL):
+    if url.scheme == "http":
+        return CurlHttpVersion.V1_1
+    return None
+
+
 def resolve_timeout(request: httpx.Request) -> float:
     extension = request.extensions.get("timeout") or {}
     for key in ("read", "connect", "pool"):
@@ -79,6 +85,10 @@ class CurlTransport(httpx.AsyncBaseTransport):
             if key.lower() not in STRIP_REQUEST_HEADERS
         }
         body = await request.aread()
+        extra = {}
+        version = http_version_for(request.url)
+        if version is not None:
+            extra["http_version"] = version
         try:
             response = await self._session.request(
                 request.method,
@@ -90,6 +100,7 @@ class CurlTransport(httpx.AsyncBaseTransport):
                 stream=True,
                 allow_redirects=False,
                 timeout=resolve_timeout(request),
+                **extra,
             )
         except Timeout as exc:
             raise httpx.ConnectTimeout(str(exc), request=request) from exc