Write adjacent photogrammetry sidecars next to captured images

[gsrunion]

OpenScan3 already persists scan metadata for captured photos, but it currently stores it under scanXX/metadata/*.json.

Proposal:

• Also write a photogrammetry-friendly adjacent sidecar next to each image.
• Example layout:
  • scan01_001.jpg
  • scan01_001.json

Suggested sidecar fields:

• project_name
• scan_index
• step
• stack_index
• azimuth_deg
• elevation_deg
• radius
• cartesian
• camera_name

Why:

• Easier downstream use with COLMAP and custom photogrammetry pipelines
• Keeps image and pose metadata colocated
• Avoids requiring tool-specific knowledge of OpenScan3's metadata/ folder layout

Notes:

• This should be additive, not a replacement for the existing metadata/ directory.

Existing OpenScan3 code:

• openscan_firmware/models/scan.py
• openscan_firmware/controllers/services/tasks/core/scan_task.py
• openscan_firmware/controllers/services/projects.py

Prototype/reference code:

• openscan-pipeline/src/pipeline_orchestrator.py
  • writes adjacent JSON sidecars with pose fields