Providing back-end owned encoder metadata

[aleksandr-voitenko]

Description

Expose backend-owned video encoder metadata through getAvailableEncoders() so Desktop no longer has to duplicate or infer encoder IDs, families, preset fields, or codec support.

This expands encoder discovery from { title, name } to include:

• id: concrete OBS encoder id used to create the encoder
• family: public Desktop-facing encoder profile key, such as x264, qsv, amd, nvenc
• preset: OBS settings field that stores the preset value
• codec: codec reported by the concrete OBS encoder
• streaming / recording: availability flags from the backend encoder table

Motivation and Context

Desktop had a partial hand-maintained copy of encoder mappings. When OBS/OSN added newer encoder IDs, Desktop could fail to resolve them and omit the concrete videoEncoder, causing invalid encoder errors for encoders such as QuickSync, AMD, AOM AV1, and SVT-AV1.

Moving this metadata into OSN makes the backend encoder table the source of truth.

Types of changes

• New feature (non-breaking change which adds functionality)