docs: Document DuckLake INSERT write support

[lukekim]

Summary

The DuckLake data connector gained INSERT INTO write support via spiceai/spiceai#10744 but the data connector docs still implied read-only. The DuckLake catalog connector docs already cover access: read_write (and read_write_create for DDL); this PR brings the data connector docs in line.

Changes

• Added a Write Support section to website/docs/components/data-connectors/ducklake.md showing access: read_write and an INSERT INTO example.
• Added write to the page's tags: frontmatter (already declared in tags.yml).
• Clarified in Limitations that UPDATE, DELETE FROM, and DDL are not supported on the data connector — users needing DDL should use the catalog connector with access: read_write_create.

vNext-only: feature shipped post-v1.11.6 so no versioned docs need updating.

Reference

Verified against spiceai/spiceai trunk:

• crates/runtime/src/dataconnector/ducklake.rs lines 363-385 — read_write_provider method
• crates/data_components/src/ducklake/writer.rs lines 174-194 — insert_into implementation (only Append and Overwrite ops; no delete_from or update)

Test plan

• cd website && npm run build passes locally
• No broken links, no undefined tags

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