Expose lightweight Django JSON endpoints for hosts, snapshots, and backup runs
using the existing admin/staff authentication boundary. Include filters for
snapshot and run inspection, return resolved snapshot base metadata, and document
the new /api/ entrypoint.
Add endpoint tests for authentication, host summaries, snapshot lineage payloads,
and run filtering.
Add a Django admin-backed management layer for pobsync configs, runs,
snapshots, and schedules. Keep the existing CLI engine as the execution
source of truth, add import/run management commands, and provide SQLite
default plus optional MariaDB Docker Compose support.
