C01: P1: service/storage foundation

[ChrisTitusTech]

Go implementation tracking epic

Selected stack: Go + Wails v2 + React/TypeScript + SQLite. Implementation starts on the next machine. Each child below is a separate PR; do not implement this epic in one PR.

Child tasks

• C01a: Domain interfaces and fixture services
  • Merged prerequisites: F01b, F03b.
  • Acceptance: R7: typed Go DTOs, canonical IDs, fixture adapter substitution, deadlines/cancellation and structured errors verified without UI or network.
• C01b: Private storage and first migration
  • Merged prerequisites: C01a.
  • Acceptance: R6: XDG paths, 0700/0600 personal storage, transactional migration and failed-upgrade restore tests; oldhelp data is untouched.

Workflow

See TASKS.md, ROADMAP.md, and CONTRIBUTING.md. Aim for 100-400 handwritten changed lines per PR; split above 600 unless inseparable. Merge prerequisites before dependents. Update task evidence and this checklist after each completed PR. Close this epic only when every child passes; optional work can remain deferred.

All tasks are not started. Live game access and publication/merge actions follow the user's explicit authorization. The planning handoff does not claim runtime validation.