phsl / new-api

- Port classic ParamOverrideEditorModal to default as standalone dialog (~3200 lines)
  with two-panel layout, drag-to-reorder, 23 operation modes, template library,
  visual/JSON dual mode, conditions management, and legacy format support
- Redesign channel drawer layout with clear visual hierarchy (CardHeading vs SubHeading)
  and bordered sub-modules for Field Passthrough and Upstream Model Detection
- Replace header override JsonEditor with plain textarea matching classic behavior
- Add searchable channel type combobox with scroll fix
- Add 100+ i18n keys across all 6 locales (en, zh, fr, ja, ru, vi)