fix: Support study metadata and instance QIDO endpoints

[sedghi]

Problem

Static DICOMweb datasets contain metadata for each individual series, but the web server does not expose the standard study-level WADO-RS endpoint:

GET /studies/{StudyInstanceUID}/metadata

Clients that retrieve metadata for an entire study therefore receive no study-level response even though all required metadata already exists in the generated series directories.

There is also a routing issue for series-instance QIDO requests:

GET /studies/{StudyInstanceUID}/series/{SeriesInstanceUID}/instances

The request is mapped to the generated instance index, but it can continue into retrieval routing instead of being served by the static index handler, resulting in a not-found response.

Solution

• Add a study metadata controller that reads every series metadata array, combines them, and returns application/dicom+json from the standard study metadata endpoint.
• Support both compressed metadata.gz and uncompressed metadata files.
• Preserve on-demand index generation when series metadata has not been generated yet.
• Serve the exact series-instance QIDO route through indexingStaticController immediately after mapping it to the generated index.
• Return an empty 404 response when a study or its metadata does not exist.

This uses the existing generated dataset layout and does not require regenerating previously created static DICOMweb data.

Validation

• Added a focused unit test that combines metadata from multiple series into one study response.
• Ran the package Jest test for the new controller.
• Ran Prettier and ESLint on the changed files.
• Hosted a generated multi-study dataset and verified study, series, instance, metadata, and frame retrieval through the web server.