DRU-388 - Issues: Project + Ticket

[chaosk]

Linear ticket: DRU-388

Summary

• Bundled Issues as druks.contrib.issues next to review and Software Factory. Root entry point issues = "druks.contrib.issues.app:Issues". prefix_tables = True, icon = "layers", no agents, workflows, or Service, and no software_factory import.
• Project, Ticket, and Comment live under backend/druks/contrib/issues/ with issues_ tables. Identifiers mint from a per-project ticket_seq (UPDATE … RETURNING); a delete does not reuse a number.
• App-owned Alembic issues_0001 (alembic_version_issues). Not folded into backend/migrations/.

Test plan

• uv run ruff check backend
• uv run ruff format --check backend
• uv pip install -e backend/tests/druks-field_notes
• uv run pytest backend/
• Roster loads app issues with prefix_tables; subjectTypes stays [] (no workflow).
• Prefix mint: DRU-1 then DRU-2; delete does not reuse; ENG-1 is independent.
• Unique name/prefix; prefix change refused after a ticket exists; ticket requires project_id.
• Empty comment list is []; init-db applies issues_0001.

Pages, write doors, and the Software Factory tracker stay on later tickets.