Merge pull request 'docs(#279): add i18n MVP close-out note' (#286) from dev/issue-279-i18n-mvp-closeout-note into main

docs/ISSUE-279-I18N-MVP-CLOSEOUT.md

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+# ISSUE-279 — i18n MVP close-out note
+
+Issue: **#279** (`[READY][#175][P5] MVP close-out note: migration/changelog + release-readiness checklist for i18n`)
+
+## Scope
+
+Dette dokument lukker MVP-sporet for issue #175 med tre konkrete ting:
+
+1. en migrationsnote for release/deploy,
+2. changelog-indhold der kan genbruges i næste release-note,
+3. en release-readiness checkliste for i18n, forankret i et verificeret snapshot af `main` ved reviewtidspunktet.
+
+Repo-state ved review-opdatering:
+- `main` peger nu på merge commit `1bc4c27` (PR #283), og inkluderer også PR #282 via merge commit `6ad5430`.
+- Denne note er opdateret mod repo-tilstanden verificeret 2026-03-13 UTC, ikke en løbende garanti for senere `main`-ændringer.
+- Denne revision afløser de tidligere snapshot-antagelser fra PR-historikken, hvor #282/#283 endnu ikke var landet.
+- Der er ingen åbne release-afklaringer tilbage for PR #282/#283; begge er allerede landet på `main`.
+
+## Current i18n MVP state on `main`
+
+Følgende er allerede til stede på `main`:
+
+- **Shared contract** i `shared/i18n/lobby.json`
+  - default locale: `en`
+  - supported locales: `en`, `da`
+  - fælles frontend/backend keyspace + fallback-regler
+- **Django bootstrap** via `partyhub/i18n_bootstrap.py` og `partyhub/settings.py`
+  - `LocaleMiddleware` aktiv
+  - `LANGUAGE_CODE` + `LANGUAGES` bootstrappes fra shared catalog
+- **Backend locale/error flow** via `lobby/i18n.py`
+  - normalisering af locale-tags
+  - locale-aware fejlpayload med `error_code`, `error`, `locale`
+  - fallback til `en` når locale eller oversættelse mangler
+- **Angular MVP wiring** via
+  - `frontend/shared/i18n/lobby-loader.ts`
+  - `frontend/angular/src/app/lobby-i18n.ts`
+  - host/player shells med locale switch og shared copy-opslag
+- **Drift/parity guardrails**
+  - `shared/i18n/key-manifest.json`
+  - `scripts/check_i18n_drift.py`
+  - frontend parity/contract tests
+- **Existing documentation/artifacts**
+  - `docs/I18N_ARCHITECTURE.md`
+  - `docs/ISSUE-175-I18N-SHARED-CONTRACT-ARTIFACT.md`
+  - `docs/ISSUE-225-BACKEND-I18N-BASELINE-ARTIFACT.md`
+  - `docs/ISSUE-257-SHARED-I18N-KEYSPACE-FRONTEND-LOADER-ARTIFACT.md`
+  - `docs/ISSUE-207-I18N-AUDIO-SMOKE-ARTIFACT.md`
+  - `docs/i18n-drift-check.md`
+
+## Migration note for release
+
+### Schema impact
+
+**Der er ingen nye Django-migrations i selve i18n-MVP-sporet på `main`.**
+
+Den i18n-relaterede leverance ligger i shared catalog, locale-bootstrap, error-payload-kontrakt, Angular wiring og test/documentation. Den kræver derfor ikke en særskilt i18n-database-migration for at gå i release.
+
+### Release/deploy expectation
+
+Selv om issue #279 ikke introducerer schemaændringer, skal release-flow stadig følge repoets generelle migreringsgate:
+
+```bash
+python manage.py makemigrations --check --dry-run
+python manage.py migrate --check --noinput
+```
+
+Hvorfor: release-policyen kræver, at vi undgår code/schema drift, og staging-smoke-suiten forventer eksplicit migration consistency check.
+
+### Praktisk migrationskonklusion
+
+Til release-notes/deploy-runbook kan i18n-sporet beskrives sådan her:
+
+- **Migration impact:** none for i18n MVP itself
+- **Deploy requirement:** run standard Django migration consistency checks anyway
+- **Rollback note:** rollback er primært kode-/asset-baseret (shared catalog, frontend bundles, backend locale resolver), ikke schema-baseret
+
+## Suggested changelog content
+
+Følgende tekst kan bruges direkte i næste unreleased/release-sektion:
+
+```markdown
+### i18n
+- Shared da/en lobby i18n contract is now wired across Django and Angular MVP flows via `shared/i18n/lobby.json`.
+- Backend error payloads expose stable locale-aware fields (`error_code`, `error`, `locale`) with fallback to English for unsupported locales.
+- Angular host/player shells now consume shared i18n copy, persist preferred locale, and keep audio-policy messaging aligned with the shared catalog.
+- Added repo guardrails for i18n drift/parity through the shared key manifest, drift checker, and focused frontend/backend contract tests.
+- Release migration impact for the i18n MVP is **none** beyond the standard Django migration consistency checks.
+```
+
+Kort version til annoterede release-notes:
+
+```markdown
+## i18n MVP close-out
+- Shared da/en contract is active across backend + Angular MVP shell.
+- Locale fallback remains `en` for unsupported requests and missing translations.
+- No i18n-specific schema migration is required; keep standard `migrate --check --noinput` in release verification.
+```
+
+## Release-readiness checklist for i18n
+
+Status er vurderet mod verificeret snapshot `main@1bc4c27` (reviewet 2026-03-13 UTC, inkl. PR #282/#283).
+
+### 1) Shared contract and locale behavior
+
+- [x] Shared catalog findes i `shared/i18n/lobby.json`.
+- [x] Default/supported locales er dokumenteret og implementeret som `en` + `da`.
+- [x] Backend bruger shared contract til locale-aware fejlbeskeder.
+- [x] Frontend/Angular bruger shared loader + shared keyspace.
+- [x] Fallback-regel til `en` er dokumenteret og testet.
+
+### 2) Verification artifacts and local checks
+
+- [x] Arkitektur-note findes: `docs/I18N_ARCHITECTURE.md`.
+- [x] Baseline artifact for issue #175 findes.
+- [x] Backend artifact for issue #225 findes.
+- [x] Frontend/shared loader artifact for issue #257 findes.
+- [x] Drift-check dokumentation findes i `docs/i18n-drift-check.md`.
+- [x] Parity artifact fra issue #277 er på `main` via PR #282 (merge commit `6ad5430`).
+
+### 3) Code readiness on current branch topology
+
+- [x] Angular MVP host/player i18n flow er på `main` (PR #281).
+- [x] Shared locale/bootstrap wiring er på `main`.
+- [x] Django i18n hardening fra issue #275 er på `main` via PR #283 (merge commit `1bc4c27`).
+- [x] PR #283 er ikke længere en separat release-afklaring; hardeningen er allerede indarbejdet på `main`.
+
+### 4) Release gate before shipping i18n as “done”
+
+- [x] PR #282 er allerede merged, så parity-artifact-status er afklaret på `main`.
+- [x] PR #283 er allerede merged, så backend hardening-status er afklaret på `main`.
+- [ ] Kør drift-check fra repo root:
+  ```bash
+  python3 scripts/check_i18n_drift.py
+  ```
+- [ ] Kør backend i18n regressions:
+  ```bash
+  . .venv/bin/activate && python manage.py test \
+    partyhub.tests_i18n_bootstrap \
+    lobby.tests.I18nResolverTests
+  ```
+- [ ] Kør frontend shared-contract/parity checks:
+  ```bash
+  cd frontend && npm test -- --run \
+    tests/lobby-loader.parity.test.ts \
+    tests/lobby-i18n.contract.test.ts
+  ```
+- [ ] Kør Angular MVP locale smoke:
+  ```bash
+  cd frontend/angular && npm test -- --run \
+    src/app/lobby-i18n.spec.ts \
+    src/app/i18n-mvp-flow-smoke.spec.ts \
+    src/app/features/host/host-shell.component.spec.ts \
+    src/app/features/player/player-shell.component.spec.ts
+  ```
+- [ ] Bekræft standard migration consistency gate:
+  ```bash
+  . .venv/bin/activate && python manage.py makemigrations --check --dry-run
+  . .venv/bin/activate && python manage.py migrate --check --noinput
+  ```
+- [ ] Følg `docs/RELEASE_POLICY.md`: staging deploy, `/healthz`, smoke-resultat og changelog-reference før tag.
+
+## Close-out conclusion
+
+**Konklusion:** i18n-MVP'en er implementeret på `main`, og issue #279 leverer den manglende release-/migration-closeout dokumentation uden nye kodeændringer i app-logikken.
+
+PR #282 (parity artifact) og PR #283 (Django i18n hardening) er nu begge merged på `main`, så close-out-noten, changelog-teksten og release-readiness-checklisten kan behandles som indbyrdes konsistente for det verificerede snapshot.
+
+Det betyder, at de resterende release-gates for i18n nu er de almindelige verificeringstrin (drift-check, backend/frontend-smoke, migrations-konsistens, staging deploy og changelog-reference) — ikke længere afklaring af om #282/#283 skal lande.