## Summary
Add a locale switcher (FR / EN) to the footer's right cluster, next to the accessibility link. Closes the user-facing i18n loop — the FR bundle has existed since the sweep PR but had no in-app entry point until now.
The switcher reads the active locale from `<html lang>` (set per locale by the build), shows the native name + a globe + chevron-down chip, and on selection rewrites the URL prefix (`/en/...` ↔ `/fr/...`) and hard-refreshes so the right bundle boots — per ADR-0019.
## Architecture
Same pattern as the theme switcher:
- **`@angular/cdk/menu`** for the trigger + roving-focus menu + escape / click-outside dismissal.
- **`ViewEncapsulation.None`** because the menu opens in an overlay portal outside the component host — BEM-style class names (`.locale-switcher__*`) keep the global emissions contained.
- Each menu item carries `[attr.lang]="locale.code"` so screen readers pronounce the native names correctly.
## Decisions worth flagging
- **Locale display names ("Français", "English") are NOT i18n-marked.** Universal switcher convention: each language is always shown in its own language. Translating them would defeat the purpose for someone trying to switch *away* from the active locale they can't read.
- **No backend, no cookie, no smart `/` redirect — yet.** The URL prefix is the source of truth in v1: the next visit lands on the same locale because the URL says so. The `__Host-portal_locale` cookie + the BFF route at `/api/preferences/locale` + the smart `/` redirect described in ADR-0019 wait for the auth flow to bring the BFF online.
- **Dev-mode limitation, accepted.** Under `nx serve`, the dev server has no locale prefix in the URL — clicking the trigger lands on a non-existent path. The switcher works against the production build (`nx run portal-shell:serve-static` or any real deploy). This matches ADR-0019: dev = source locale, locale switching is a built-bundle concern.
- **Touch target.** Visible height stays at ~28 px to fit the 40 px footer; vertical padding extends the tap area to **44 px**, meeting the ADR-0016 AAA minimum without inflating the footer.
## Translation choices
Two new i18n keys:
| Key | Source (EN) | Target (FR) |
|---|---|---|
| `@@locale.trigger.aria` | `Language: <name> (change language)` | `Langue : <name> (changer de langue)` |
| `@@locale.menu.aria` | `Language` | `Langue` |
## Test plan
- [x] `pnpm exec nx run-many -t lint test build --projects=portal-shell` — green. **40 / 40 specs** (+5: four new for `LocaleSwitcher`, one for the footer embedding).
- [x] Production build emits both locales; spot-checked the FR bundle for "Langue", "changer de langue", and the absence of "Language:" leakage.
- [ ] Manual: build prod + serve-static → on `/en/`, click switcher → lands on `/fr/`; widget shows "Français"; reload stays in FR.
- [ ] Manual: keyboard the trigger → ENTER opens, arrows navigate, ENTER selects, ESC closes; focus returns to trigger on close.
- [ ] Manual: screen reader announces both languages with the right pronunciation (`<button lang="fr">Français</button>` is announced with the FR voice).
- [ ] Manual: query/hash preserved across switch (`/en/accessibility?foo=bar` → `/fr/accessibility?foo=bar`).
## What this PR explicitly does NOT do
- BFF route `/api/preferences/locale` + `__Host-portal_locale` cookie.
- Smart `/` redirect (cookie → Accept-Language → fr) — that's reverse-proxy / BFF work.
- CI gate on missing translations.
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Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #95
julien
192cc483b6