Switch photo compression from Go stdlib to libvips
Replaced Go's native image pipeline with libvips for photo compression. This results in significantly lower peak RAM usage and more aggressive memory release back to the OS.

Skip unnecessary compression for small/incompressible photos
Photos below a size threshold or with low compression ratio are now passed through directly. This saves processing time and preserves original quality.
Add log messages for app-updates endpoints
Added structured logging to app-update API endpoints for better observability and debugging in production.

