Update and expand AWS Database node icons (add missing services)

Summary

The aws.database node set is out of date with the current AWS architecture icon set. Several database services shipped by AWS have no corresponding node, and a number of existing icons predate the latest AWS icon refresh. This issue tracks bringing resources/aws/database/ (and the generated diagrams/aws/database.py + docs) up to date.

Missing services (should be added — 31)

Aurora engine variants (currently only a generic Aurora / AuroraInstance exist):

• AuroraAmazonRDSInstance, AuroraAmazonRDSInstanceAlternate, AuroraAmazonAuroraInstanceAlternate
• AuroraMysqlInstance / AuroraMysqlInstanceAlternate
• AuroraPostgresqlInstance / AuroraPostgresqlInstanceAlternate
• AuroraMariadbInstance / AuroraMariadbInstanceAlternate
• AuroraOracleInstance / AuroraOracleInstanceAlternate
• AuroraSqlServerInstance / AuroraSqlServerInstanceAlternate
• AuroraPiopsInstance
• AuroraTrustedLanguageExtensionsForPostgresql

DocumentDB:

• Documentdb (alias DocDB), DocumentdbElasticClusters

DynamoDB:

• DynamodbAmazonDynamodbAccelerator (current DAX icon)
• DynamodbStream, DynamodbStandardAccessTableClass, DynamodbStandardInfrequentAccessTableClass

ElastiCache:

• ElasticacheForValkey

Keyspaces:

• Keyspaces (alias Cassandra)

Oracle:

• OracleDatabaseAtAWS (Oracle Database@AWS)

RDS:

• RDSProxyInstance / RDSProxyInstanceAlternate
• RDSMultiAz, RDSMultiAzDbCluster
• RDSBlueGreenDeployments, RDSOptimizedWrites
• RDSTrustedLanguageExtensionsForPostgresql

DMS:

• DatabaseMigrationServiceDatabaseMigrationWorkflowOrJob

Icons that should be refreshed (29)

Existing services whose PNGs predate the current AWS icon set: Aurora, AuroraInstance, Database, DatabaseMigrationService (+ workflow), DocumentdbMongodbCompatibility, Dynamodb (+ DynamodbDax, DynamodbTable, DynamodbItem(s), DynamodbAttribute(s), DynamodbStreams, DynamodbGlobalSecondaryIndex), Elasticache (+ cache-node, for-memcached, for-redis), KeyspacesManagedApacheCassandraService, Memorydb, Neptune, RDS, RDSInstance, RDS{Mysql,Postgresql,Mariadb,Oracle,SqlServer}Instance, Timestream.

Notes / potential behavior changes

• DAX alias: AWS now ships a dedicated DynamoDB Accelerator icon (DynamodbAmazonDynamodbAccelerator). If DAX is repointed to it, the existing DynamodbDax class should be preserved for backward compatibility.
• Suggested new aliases: DocDB, ElastiCacheForValkey, Cassandra, MemoryDB, OracleDB, RDSProxy.

Acceptance criteria

• All missing services above have node classes
• Icons regenerated via autogen.sh (not hand-edited)
• docs/nodes/aws.md and website icon mirror kept in sync
• Tests pass (test_resources_exist_and_render)