feat(i18n): add Azerbaijani language support and translations (#2134)

## Launch Checklist

- [x] Adds Azerbaijani (`az`) as a supported UI language, following the
same pattern as the existing Turkish (`tr`) locale.
- [x] `src/locales/az/translation.json` — full translation, 202 keys
(matches `tr`/`de` key set exactly).
- [x] Registered `az` in `i18next.config.ts` (`locales` array) and
`src/i18n.ts` (`supportedLanguages`), alphabetically ordered.
- [x] Added `az` row to the `src/locales/README.md` contributors table.
- [ ] Link to related issues.
- [ ] Include before/after visuals or gifs if this PR includes visual
changes. (N/A — translation-only change, no UI layout changes.)
- [ ] Write tests for all new functionality. (N/A — no new
functionality, translation strings only.)
- [ ] Add an entry to `CHANGELOG.md` under the `## main` section. (Not
done — the prior Turkish locale PR (#1886) did not add a CHANGELOG entry
either, so following existing precedent.)

Terminology used consistently throughout: Layer → Qat, Style → Üslub,
Source → Mənbə, Zoom → Yaxınlaşma, Filter → Süzgəc.

src/locales/README.md

@@ -46,6 +46,7 @@ The following users can help you with the relevant languages:
 
 | ISO Code | Language           | User                                       |
 |----------|--------------------|--------------------------------------------|
+| az       | Azerbaijani        | [@jamalkamaladdin](https://github.com/jamalkamaladdin) |
 | de       | German             | [@josxha](https://github.com/josxha)       |
 | en       | English            | [@HarelM](https://github.com/HarelM)       |
 | fr       | French             | [@lhapaipai](https://github.com/lhapaipai) |