Replace fixed primary/secondary hybrid dropdowns with an ordered list
of all 5 download sources. Users enable/disable each source and reorder
with up/down arrows to set download priority. Sources are tried in
order until one returns results.
- New hybrid_order config field (backward compat with legacy primary/secondary)
- Download orchestrator loops ordered list with per-source error handling
- Sortable source list UI with icons, toggle switches, priority numbers
- Source-specific settings shown for all enabled hybrid sources
- Seamless migration from legacy 2-source to N-source format
fc4e16337a
