docs: add missing libSQL row to test-database table - #1637

Summary

Closes #1265.

Two changes to the local test-database table in docs/providers/README.md, both from the issue:

1. libSQL row added. | libSQL | \libsql` | localhost | 18080 | none | none | none | — |, placed after the Redis row and before Couchbase, matching the order the paragraph above the table counts the engine containers in. Port 18080is bold like OpenSearch's9201, because it is not the engine's usual port: database-compose.ymlmaps the container's8080to18080so it does not collide with Trino. No user, password or token, no TLS, no profile — the compose service carries noprofiles:key anddocs/providers/libsql.md` describes the auth-free local mode.

2. *none* in the Profile column replaced with the em dash the PostgreSQL row uses. The issue named the Prometheus, Apache Kafka, etcd and Neo4j rows (lines 284-287 of the pinned commit). Since then main has gained more rows carrying the same wrong placeholder — InfluxDB 1.x, InfluxDB 2.x, InfluxDB 3 (SQL), Oxia, Milvus and Qdrant — so all ten are fixed here, which is what the "Done when" criterion ("every row that needs no profile shows the same placeholder") asks for. *none* is defined under the table as "leave the field empty", which cannot apply to a column that is not a connection field.

Only docs/providers/README.md changes. The User, Password and Database columns keep their *none* placeholders — those are connection fields and the placeholder is correct there.

Verification

• git diff --stat: one file, 11 insertions, 10 deletions.
• Every changed Profile cell was checked against the base table: the em dash is the placeholder used by PostgreSQL, MySQL, Oracle, Db2, SQL Server, MongoDB, Redis, Couchbase, ClickHouse, Elasticsearch, OpenSearch, Trino, Databend and Cassandra, i.e. every row that needs no profile.
• The libSQL values are read off database-compose.yml (service libsql, port mapping 18080:8080, no profiles: key) and docs/providers/libsql.md (auth-free local mode, no TLS) rather than assumed.
• Markdown table column count checked per row: eight cells, matching the header.
• No test or lint gate applies to a docs-only change; Lint, Typecheck and Build and Unit & Integration Tests are left to run on the PR.