fix(models): replace postgresql.UUID with database-agnostic UUID (#2495)

[mrveiss]

Summary

• Replaces sqlalchemy.dialects.postgresql.UUID with sqlalchemy.types.Uuid in 5 model files
• Matches pattern from PR fix(backend): replace postgresql.UUID with dialect-neutral Uuid (#2402) #2424 for workflow_permission.py
• sqlalchemy.types.Uuid is SQLAlchemy 2.0's dialect-neutral type: native UUID on PostgreSQL, 32-char string on SQLite
• Enables SQLite compatibility for dev/test environments

Files Changed

• autobot-backend/user_management/models/base.py — import + type_annotation_map + TenantMixin
• autobot-backend/user_management/models/role.py — import + 9 columns
• autobot-backend/user_management/models/mfa.py — import + 2 columns
• autobot-backend/models/agent.py — import + 1 column
• autobot-backend/models/agent_org.py — import + 1 column

Note

6 additional model files also use postgresql.UUID alongside JSONB — these need a separate fix (split import). Not in scope for this PR.

Closes #2495

Test plan

• No remaining postgresql.UUID in the 5 fixed files
• Python AST parse passes for all changed files
• Backend starts without import errors

[github-actions]

✅ SSOT Configuration Compliance: Passing

🎉 No hardcoded values detected that have SSOT config equivalents!