feat(node): expose allowExternalBlobOutsideBases in Table.add (#4317)

## Summary

- Add `allowExternalBlobOutsideBases` to the Node `AddDataOptions` and
forward it through N-API to the Rust `AddDataBuilder`.
- Document its default and local-only external blob behavior.
- Cover URI strings and URI objects, option scoping, progress callbacks,
overwrite mode, and remote rejection.

## Validation

- `pnpm test --runInBand` (21 suites passed, 1 skipped; 908 tests
passed, 6 skipped)
- `pnpm lint-ci`
- `pnpm tsc`
- `pnpm run docs`
- `cargo fmt --all -- --check`
- `CC=clang cargo clippy --profile ci -p lancedb-nodejs --all-features
-- -D warnings`

Fixes #4267

docs/src/js/interfaces/AddDataOptions.md

@@ -10,6 +10,22 @@ Options for adding data to a table.
 
 ## Properties
 
+### allowExternalBlobOutsideBases?
+
+```ts
+optional allowExternalBlobOutsideBases: boolean;
+```
+
+Whether blob URIs outside registered external bases may be written.
+
+Defaults to `false`. This option is supported only for local/native
+tables; remote tables return an error when it is enabled. An enabled write
+stores the absolute URI reference without registering a base or copying
+the external object into the database. The object must remain accessible
+when the blob is read later.
+
+***
+
 ### mode
 
 ```ts