feat(studio): dual-source roadmap — local Postgres layer (CS-76 phase A)

[RudneyForti]

Summary

Phase A of CS-76: the Studio roadmap becomes dual-source. Postgres now owns the editable pre-PR layer (Backlog / Bloqueado / Em andamento); the git board (docs/cs-board.json) remains the authoritative done archive, written only by the roadmap-sync Action. The UI never rewrites the git board — the two writers stop fighting.

Changes

• RoadmapCard model (Prisma): local layer keyed by csNumber (the upsert/join identity)
• assembleBoard (lib/kanban.ts, pure + tested): merges git done cards with local cards, git-wins precedence when a CS was promoted
• getKanbanBoard: reads git file + Postgres in parallel and assembles
• saveKanbanBoard: persists only local-column cards to Postgres (upsert by CS + prune removed); git file untouched
• UI locks: git-owned cards are non-draggable, drop into/out of git columns is cancelled, card modal opens read-only for git-owned cards regardless of assisted mode
• Card creation: CS number now required (blank numbers collided on the upsert key); duplicate CS rejected
• Backfill script scripts/roadmap-backfill-local.mjs (idempotent, ON CONFLICT DO NOTHING) — already run on dev: 17 cards seeded
• Board subtitle now states both sources: "N planejados Postgres · M concluídos git"

Checklist

• Link to feature/issue: CS-76
• Description of changes included above
• List of additions documented
• All existing tests are passing (92)
• New tests were added for this change (assembleBoard, isLocalColumn, local persistence routing)
• Agent Smith validated behavior (browser round-trip: edit persisted to Postgres, git file untouched, git status clean)
• No regressions observed

References

CS-76 (phase A of 3 — phase B adds the GitHub source + Revisão column, phase C server-side enforcement + AGENTS.md)