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.

i18next.config.ts

@@ -1,7 +1,7 @@
 import { defineConfig } from "i18next-cli";
 
 export default defineConfig({
-  locales: ["de", "fr", "he", "it", "ja", "ko", "tr", "zh"],
+  locales: ["az", "de", "fr", "he", "it", "ja", "ko", "tr", "zh"],
   extract: {
     input: ["src/**/*.{js,jsx,ts,tsx}"],
     output: "src/locales/{{language}}/{{namespace}}.json",