Add defineConfig() identity function for type inference. Rewrite loadConfig
to use dynamic import() instead of YAML parsing. Update all call sites
(main.ts, cli.ts, test.ts, vite-plugin.ts) and the scaffolder. Add
./config package export. Dockerfile template uses --experimental-strip-types
for native Node 25 TS support.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Resync endpoint sets repos to pending then calls runBackfill
instead of triggerAutoBackfill, using the same batch worker pool
- runBackfill returns record count; restart only if work was done
- Shared runBackfillAndRestart function used by both boot and resync

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>