feat(i18n): add Turkish (tr) locale support

Add complete Turkish translation across all 7 i18n namespaces:
- common: actions, playback controls, locale metadata
- launch: HUD tooltips, audio/webcam controls, source selector
- editor: error messages, export, project, recording permissions
- dialogs: export progress, trim tutorial, unsaved changes, file dialogs
- settings: all panels (zoom, speed, trim, layout, effects, background,
  crop, export, annotations, custom fonts, language, audio)
- shortcuts: keyboard shortcuts panel and all actions
- timeline: toolbar buttons, hints, labels, errors, success messages

Also adds "tr" to SUPPORTED_LOCALES config and i18n validation script.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/i18n-check.mjs

@@ -11,7 +11,7 @@ import path from "node:path";
 
 const LOCALES_DIR = path.resolve("src/i18n/locales");
 const BASE_LOCALE = "en";
-const COMPARE_LOCALES = ["zh-CN", "es"];
+const COMPARE_LOCALES = ["zh-CN", "es", "tr"];
 
 function getKeys(obj, prefix = "") {
 	const keys = [];