1. Increase garminOauth1Token and garminOauth2Token max length from
5000 to 20000 characters to accommodate encrypted OAuth tokens.
Add logic to update existing field constraints in addUserFields().
2. Fix flaky pocketbase-harness e2e test by adding retry logic with
exponential backoff to createAdminUser() and createTestUser().
Handles SQLite database lock during PocketBase startup migrations.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>