feat(dynamodb): item CRUD, batch write, and JSON editor UI (#69)

[saurabhkhadsangTV]

Supersedes branch from #107 (head fork was recreated); delivered as one squashed commit on current main.

Implements create / update / delete for DynamoDB items, batch import and bulk delete, JSON editor with plain vs DynamoDB attribute-value modes, and read-only middleware fix so item write POSTs are not treated like POST .../query.

Includes feedback from #107 review: invalidate item count cache after batch writes even when UnprocessedItems is non-empty; warning toasts when import/bulk delete leaves unprocessed items.

Backend

• POST / PUT /api/dynamodb/tables/{name}/items — put_item (item + item_format: dynamodb | plain)
• DELETE /api/dynamodb/tables/{name}/items — delete_item
• POST /api/dynamodb/tables/{name}/items/batch — batch write (≤25 ops)

Frontend

Toolbar (new/import), row actions, marshal toggle, useHealth for writes.

Tests

tests/test_dynamodb_routes.py, tests/test_readonly_middleware.py, UI dynamodb tests.

Verify

Resources → DynamoDB → create / scan / edit / delete / import / bulk delete; STACKPORT_ALLOW_WRITES=false hides writes / returns 403.

[DaviReisVieira]

LGTM! Both issues from the #107 review are addressed:

1. Cache invalidation now runs unconditionally after batch_write_item — partial success no longer leaves stale counts. Nice addition of test_batch_write_partial_invalidates_cache too.

2. Frontend now shows warning toasts when import or bulk delete has unprocessed items. The countUnprocessed helper is clean.

All checks pass (22 backend tests, 176 frontend tests, typecheck clean). Ship it! 🚀