docs: port JDBC readonly profiles and JSON type notes from upstream

[mintlify]

Summary

Ports upstream clickhouse-docs#6416 ("[Java] update JDBC docs.") to the Mintlify docs.

Changes

• integrations/language-clients/java/jdbc.mdx:
  • Adds a Readonly Profiles note under connection configuration, recommending readonly=2 when users need to pass format settings (e.g. reading JSON as String). Links to /operations/settings/constraints-on-settings#read-only.
  • Adds a JSON Type section under special types covering the default Map<String, Object> mapping, the jdbc_read_json_as_string / OUTPUT_FORMAT_BINARY_WRITE_JSON_AS_STRING option to read JSON as String, and JSON number quoting behavior in ClickHouse 25.8+ vs older servers (output_format_json_quote_64bit_integers, _64bit_floats, _decimals).

Content ported verbatim from the upstream diff. i18n translation directories were not touched per instructions.

Context

Upstream merge commit: 900f85b1f90048eb25727af0e89b37b9b73e57b0. Closes ClickHouse/clickhouse-java#2760 upstream.

Note: mint validate and mint broken-links both timed out locally on this repo, so the changes were not validated through the CLI — they are pure additive markdown/code-fence content with one internal link that resolves to an existing slug and anchor.

---

Note

Low Risk
Documentation-only additive content in the Java JDBC integration page; no runtime or configuration code changes.

Overview
Ports upstream JDBC documentation into integrations/language-clients/java/jdbc.mdx.

Under Connection Properties, a Readonly Profiles note explains why the driver avoids default connection settings and recommends readonly=2 when users need format-related server settings (e.g. reading JSON as String), with a link to the read-only settings constraints doc.

Under Special Types, a new JSON Type section documents the default Map<String, Object> mapping with an example, the OUTPUT_FORMAT_BINARY_WRITE_JSON_AS_STRING / connection-property path to read JSON as String, and JSON number quoting behavior on ClickHouse 25.8+ versus older servers via output_format_json_quote_* server settings.

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