Security fixes:
- Add startup warning for default JWT secret in config
- Add enum validation for priority, recipient_type, channel fields
- Add pagination size cap (max 100) via safe_page_size()
- Return generic "权限不足" instead of specific permission names
Compilation fixes:
- Fix missing standard fields in ActiveModel for tokens/process_variables
- Fix migration imports for Statement/DatabaseBackend/Uuid
- Add version_field to process_definition ActiveModel
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>