feat(api): typed OpenAPI client consumed by the SPA (Phase 0 finish)

[dnplkndll]

What changed

Finishes Phase 0's typed-client gate: the OpenAPI schema + a typed TypeScript client are committed, the SPA consumes the client, and CI drift-gates it against the live API.

Most of the plumbing already existed (drf-spectacular configured, /api/schema/ + swagger/redoc routes, gen_api_client.sh, a CI step). What was missing — and is delivered here — is the committed client + actual consumption + a drift gate.

Committed artifacts (source of truth)

• generated/openapi.yaml — OpenAPI 3 schema from frepplectl spectacular --validate (covers the DRF input/master-data CRUD).
• frontend/lib/api-types.ts — typed client (openapi-typescript, pinned 7.0.0). Now committed (it was gitignored before it had a consumer) so the SPA builds anywhere without a Django runtime.

SPA consumption

• frontend/lib/apiSchema.ts — typed entrypoint re-exporting the order schemas + StatusCa7Enum.
• orders.ts — ORDER_STATUSES … as const satisfies readonly OrderStatus[] type-couples the Orders screen to the API enum: a renamed/removed status in Django now breaks the frontend typecheck. (records.ts Column.options widened to readonly.)
• ✅ Frontend tsc --noEmit clean + 73 vitest tests pass.

Drift gate

• tools/modernization/gen_api_client.sh regenerates schema → client → strict typecheck, pinning openapi-typescript to the frontend's version so CI regeneration is byte-identical.
• ubuntu24.yml runs it then git diff --exit-code — the committed schema/client can't drift from the live API.

Scope notes

• The streaming output endpoints (pivot/pegging) are plain Django views (no DRF serializer) → absent from the schema by design; they keep hand-written shapes (dynamic time-bucket columns).
• The typed client immediately earned its keep, surfacing two contract nuances (the ManufacturingOrder schema has no item field; bulk-CRUD operationId collisions) — noted in the plan as non-blocking cleanups.

Large diff is the two generated files (~25k lines) — review the hand-written apiSchema.ts / orders.ts / script / workflow. No UI change → no screenshots. Per convention, not auto-merging.

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Self-review pass

• Squashed to 2 clean commits: hand-written code/config/docs, then the generated artifacts (so reviewers can skip the ~25k generated lines).
• Trimmed apiSchema.ts to the consumed surface (removed speculative OrderPatch/EditableOrderField).
• gen_api_client.sh reads the openapi-typescript version from either dependencies or devDependencies (robustness).
• Confirmed the ManufacturingOrder serializer genuinely omits item (the MO grid's item is view/annotation-derived) — kept as a documented non-blocking finding.
• No visual change (compile-time type coupling only) → no screenshots.