feat(i18n): add Turkish (tr) language support (#678)

* feat(i18n): add Turkish (tr) language support

Add comprehensive Turkish localization for the UI, following the
existing i18n pattern established by Japanese (#384), Russian (#514),
and German (#525) language support.

Changes:
- Add Turkish translation files for all 7 namespaces
  (auth, chat, codeEditor, common, settings, sidebar, tasks)
- Register Turkish locale in config.js with all resources
- Add Turkish entry to languages.js (value: tr, nativeName: Türkçe)
- Update .gitignore to allow src/i18n/locales/tr/tasks.json
  (matches existing en/ja/ru/de exceptions)

Translation details:
- 934 total strings translated (100% coverage, matches en.json key count)
- Translated by a native Turkish speaker with software engineering
  background; terminology reviewed against conventional Turkish
  tech community usage.
- Technical terms kept in English per Turkish dev community norms:
  Claude, Cursor, Codex, Gemini, CLI, MCP, PRD, JSON, YAML, stdio,
  http, commit, branch, token, prompt, minimap, sandbox, YOLO.
- Informal second-person singular (\"sen\") used throughout — fits the
  developer-facing nature of the UI.
- All interpolation placeholders preserved exactly (e.g. {{count}},
  {{projectName}}, {{email}}).
- i18next plural keys (_one/_other) kept intact.

Verification:
- Key structure parity with en.json confirmed (jq paths diff empty)
- All 38 unique interpolation variables preserved
- npm run build passes cleanly

* docs(readme): add Turkish README and language switcher links

Add README.tr.md — full Turkish translation of the main README,
following the structure of existing README.de.md / README.ja.md /
README.ko.md / README.ru.md / README.zh-CN.md.

Update the language switcher row in all 6 existing README variants
to include a Turkish link (matches the pattern used by #534 for the
German language link addition).

---------

Co-authored-by: Simos Mikelatos <simosmik@gmail.com>

README.de.md

@@ -15,7 +15,7 @@
   <a href="https://trendshift.io/repositories/15586" target="_blank"><img src="https://trendshift.io/api/badge/repositories/15586" alt="siteboon%2Fclaudecodeui | Trendshift" style="width: 250px; height: 55px;" width="250" height="55"/></a>
 </p>
 
-<div align="right"><i><a href="./README.md">English</a> · <a href="./README.ru.md">Русский</a> · <b>Deutsch</b> · <a href="./README.ko.md">한국어</a> · <a href="./README.zh-CN.md">中文</a> · <a href="./README.ja.md">日本語</a></i></div>
+<div align="right"><i><a href="./README.md">English</a> · <a href="./README.ru.md">Русский</a> · <b>Deutsch</b> · <a href="./README.ko.md">한국어</a> · <a href="./README.zh-CN.md">中文</a> · <a href="./README.ja.md">日本語</a> · <a href="./README.tr.md">Türkçe</a></i></div>
 
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