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/i18n.ts

@@ -4,6 +4,7 @@ import resourcesToBackend from "i18next-resources-to-backend";
 import { initReactI18next } from "react-i18next";
 
 export const supportedLanguages = {
+  "az": "Azərbaycan",
   "de": "Deutsch",
   "en": "English",
   "fr": "Français",