fix(scheduler,config): preserve ENV schedule; add AUTO_MIRROR_REPOS auto-mirroring

- Prevent Automation UI from overriding schedule:
      - mapDbScheduleToUi now parses intervals robustly (cron/duration/seconds) via parseInterval
      - mapUiScheduleToDb merges with existing config and stores interval as seconds (no lossy cron conversion)
      - /api/config passes existing scheduleConfig to preserve ENV-sourced values
      - schedule-sync endpoint uses parseInterval for nextRun calculation
  - Add AUTO_MIRROR_REPOS support and scheduled auto-mirror phase:
      - scheduleConfig schema includes autoImport and autoMirror
      - env-config-loader reads AUTO_MIRROR_REPOS and carries through to DB
      - scheduler auto-mirrors imported/pending/failed repos when autoMirror is enabled before regular sync
      - docker-compose and ENV docs updated with AUTO_MIRROR_REPOS
  - Tests pass and build succeeds

docker-compose.yml

@@ -57,6 +57,7 @@ services:
       - SCHEDULE_ENABLED=${SCHEDULE_ENABLED:-false}
       - GITEA_MIRROR_INTERVAL=${GITEA_MIRROR_INTERVAL:-8h}
       - AUTO_IMPORT_REPOS=${AUTO_IMPORT_REPOS:-true}
+      - AUTO_MIRROR_REPOS=${AUTO_MIRROR_REPOS:-false}
       # Repository Cleanup Configuration
       - CLEANUP_DELETE_IF_NOT_IN_GITHUB=${CLEANUP_DELETE_IF_NOT_IN_GITHUB:-false}
       - CLEANUP_ORPHANED_REPO_ACTION=${CLEANUP_ORPHANED_REPO_ACTION:-archive}