Introduce a `/tracks/:id/flac` endpoint and `open_cmaf_stream` client method to enable incremental decryption and caching of FLAC audio. Refactor segment decryption into a reusable helper and stream decrypted frames via a bounded tokio channel. Add `tokio-util` as an optional dependency, update the `pmoserver` feature, and implement conditional routing for local proxy versus direct API access. Update the architecture roadmap to document these improvements.
Introduces a new CMAF streaming module for Qobuz that handles progressive segment fetching and full-track decryption. The implementation adds HKDF session key derivation, AES-128-CBC key unwrapping, and AES-128-CTR frame decryption, alongside an ISO BMFF parser for extracting FLAC headers and segment metadata. It also integrates automatic session renewal with double-checked locking, a generic async retry mechanism for transient HTTP errors, and centralized error handling. Finally, it exposes `CmafStreamInfo` and async streaming methods in the public API, updating cryptographic dependencies accordingly.
