BaseCard and UserCard schema improvements + local dynamodb smoke tests

[cboiteux2765]

Description

Adds the BaseCard/UserCard persistence contract and a server-side DynamoDB implementation for saving and resetting vocabulary cards.

• Replaces the legacy flat frontend card type with typed BaseCard, UserCard, nested content, annotations, and warnings contracts.
• Defines the lookup Lambda response contract as { card: BaseCard } and updates the lookup UI to consume it.
• Adds POST /api/cards to create a user-owned card from an already-available BaseCard, without calling the lookup Lambda.
• Adds POST /api/cards/:cardId/reset to restore editable content from the stored BaseCard while preserving userId, cardId, createdAt, baseRef, notes, and warnings.
• Uses the low-level DynamoDB SDK and explicit JSON-to-AttributeValue conversion (S, N, BOOL, M, L, and NULL).
• Adds local DynamoDB smoke tests in TypeScript and Boto3, plus setup and test documentation.

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update

How did you test this?

With DynamoDB Local running at http://127.0.0.1:8000:

cd frontend
$env:DYNAMODB_ENDPOINT = 'http://127.0.0.1:8000'
npm run dynamodb:smoke
py -3.12 scripts/dynamodb_boto3_smoke.py

Results:

• npm run build completed successfully.
• The TypeScript smoke test created local BaseCards and UserCards tables, saved a sample BaseCard-derived UserCard, printed the raw DynamoDB wrappers, simulated an incorrect definition, and verified reset restored the BaseCard definition while retaining the user note.
• The Boto3 smoke test directly inserted the BaseCard and converted UserCard with the low-level put_item API. It verified content is an M, content.definitions is an L, definition text is an S, and revision is an N.
• The AWS SDK emitted a non-blocking Node 20 future-support warning; it did not affect either test.

Checklist

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• New and existing unit tests pass locally with my changes.

Next steps

• Implement or update the deployed word-lookup Lambda to return the shared { card: BaseCard } payload.
• Configure AWS_REGION, USER_CARDS_TABLE_NAME, and BASE_CARDS_TABLE_NAME, then grant the deployed server runtime least-privilege DynamoDB access.
• Add an authenticated end-to-end test for lookup Lambda -> save endpoint -> UserCards -> reset endpoint -> BaseCards.
• Wire the saved-cards UI to the new UserCard API and expose save/reset actions in the interface.
• Add request validation beyond the current structural BaseCard check before production rollout.

GenAI usage

• What model(s) did you use? Codex (GPT-5).
• Percent of AI-written code? Approximately 90%; reviewed and tested locally.
• Any drawbacks? Generated code still requires review for project-specific IAM, deployment configuration, validation policy, and API compatibility. Actual end-to-end testing will be done when Lambda works and returns dictionary words put into the baseCard schema.
• Main prompt summary: Implement the supplied BaseCard/UserCard schemas, DynamoDB storage conversion, save/reset endpoints, and local DynamoDB tests without depending on the lookup Lambda.

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