Remove database migrations after direct schema fixes

Changes:
- Removed all migration code from server.js
- Database schema fixed directly via MySQL:
  * Dropped users.role column (SSO only)
  * Dropped users.password column (SSO only)
  * Added executions.started_by column
  * Added workflows.created_by column
  * All tables now match expected schema
- Server startup will be faster without migrations

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.gitignore

@@ -30,3 +30,6 @@ Thumbs.db
 *.swp
 *.swo
 *~
+
+# Claude
+Claude.md