feat: [WRA-17] add DynamoDB FDW

[burmecia]

What kind of change does this PR introduce?

This PR is to add a new DynamoDB FDW.

What is the current behavior?

There is no DynamoDB FDW.

What is the new behavior?

A new DynamoDB FDW is added with data read and modify capability.

Additional context

N/A

[Copilot]

Pull request overview

Adds a new native AWS DynamoDB Foreign Data Wrapper (FDW) to the Wrappers extension, including local DynamoDB test infra and end-user documentation.

Changes:

• Introduces dynamodb_fdw module with scan/query, modify (insert/update/delete), and IMPORT FOREIGN SCHEMA support.
• Adds pgrx tests plus DynamoDB Local docker-compose services + seeding script for CI.
• Updates repo docs/catalog navigation and feature flags/dependencies to include the new FDW.

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 12 comments.

Show a summary per file

File	Description
wrappers/src/fdw/mod.rs	Registers the new dynamodb_fdw module behind a feature flag.
wrappers/src/fdw/dynamodb_fdw/mod.rs	Declares DynamoDB FDW modules and error type wiring.
wrappers/src/fdw/dynamodb_fdw/dynamodb_fdw.rs	Core FDW implementation: client setup, scan/query paging, modify, import schema, validator.
wrappers/src/fdw/dynamodb_fdw/conv.rs	DynamoDB AttributeValue ↔︎ wrappers Cell conversions.
wrappers/src/fdw/dynamodb_fdw/tests.rs	Integration tests covering scan, pushdown, type mapping, writes, and import schema.
wrappers/src/fdw/dynamodb_fdw/README.md	FDW README + changelog entry.
wrappers/dockerfiles/dynamodb/init.sh	Seeds DynamoDB Local tables/items used by tests.
wrappers/.ci/docker-compose-native.yaml	Adds DynamoDB Local + init container to CI compose stack.
wrappers/Cargo.toml	Adds dynamodb_fdw feature and optional dependency on aws-sdk-dynamodb.
README.md	Adds DynamoDB to the top-level FDW catalog table.
mkdocs.yaml	Adds DynamoDB doc page to MkDocs navigation.
docs/catalog/index.md	Adds DynamoDB row to catalog capability matrix.
docs/catalog/dynamodb.md	New DynamoDB FDW documentation page.
Cargo.lock	Locks new Rust dependencies pulled in for DynamoDB support.

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