feat(i18n): Implement and refine language selection feature

Introduces a language selection option in settings, allowing users to manually choose an application language or revert to automatic system locale detection. This includes UI updates, settings integration, and improved language detection logic.

Assets/Translations/en.json

@@ -76,7 +76,8 @@
         },
         "select": {
           "label": "Application Language",
-          "description": "Select the language used in the application's interface."
+          "description": "Select the language used in the application's interface.",
+          "auto-detect": "Automatic"
         }
       }
     },

Commons/I18n.qml

@@ -7,10 +7,11 @@ import qs.Commons
 
 Singleton {
   id: root
-  property string debugForceLanguage: ""
+
 
   property bool isLoaded: false
   property string langCode: ""
+  property string systemDetectedLangCode: ""
   property var availableLanguages: []
   property var translations: ({})
   property var fallbackTranslations: ({})
@@ -158,48 +159,40 @@ Singleton {
       return
     }
 
-    if (Settings.isDebug && debugForceLanguage !== "") {
-      Logger.d("I18n", `Debug mode: forcing language to "${debugForceLanguage}"`)
-      if (availableLanguages.includes(debugForceLanguage)) {
-        setLanguage(debugForceLanguage)
-        return
-      } else {
-        Logger.w("I18n", `Debug language "${debugForceLanguage}" not available in [${availableLanguages.join(', ')}]`)
-      }
-    }
+    var detectedLang = ""
 
-    // Check for user-defined language setting
-    if (Settings.data.general.language !== "" && availableLanguages.includes(Settings.data.general.language)) {
-      Logger.d("I18n", `User-defined language found: "${Settings.data.general.language}"`)
-      setLanguage(Settings.data.general.language)
-      return
-    }
-
-    // Detect user's favorite locale - languages
+    // First, determine the system's preferred language
     for (var i = 0; i < Qt.locale().uiLanguages.length; i++) {
       const fullUserLang = Qt.locale().uiLanguages[i]
 
-      // Try full code match (such as zh CN, en US)
       if (availableLanguages.includes(fullUserLang)) {
-        Logger.d("I18n", `Exact match found: "${fullUserLang}"`)
-        setLanguage(fullUserLang)
-        return
+        detectedLang = fullUserLang
+        break
       }
 
-      // If full code match fails, try short code matching (such as zh, en)
       const shortUserLang = fullUserLang.substring(0, 2)
       if (availableLanguages.includes(shortUserLang)) {
-        Logger.d("I18n", `Short code match found: "${shortUserLang}" from "${fullUserLang}"`)
-        setLanguage(shortUserLang)
-        return
+        detectedLang = shortUserLang
+        break
       }
-
-      Logger.d("I18n", `No match for system language: "${fullUserLang}"`)
     }
 
-    // Fallback to first available language (preferably "en" if available)
-    const fallbackLang = availableLanguages.includes("en") ? "en" : availableLanguages[0]
-    setLanguage(fallbackLang)
+    // If no system language is found among available languages, fallback
+    if (detectedLang === "") {
+      detectedLang = availableLanguages.includes("en") ? "en" : availableLanguages[0]
+    }
+
+    root.systemDetectedLangCode = detectedLang
+    Logger.d("I18n", `System detected language: "${root.systemDetectedLangCode}"`)
+
+    // Now, apply the language: user-defined, then system-detected
+    if (Settings.data.general.language !== "" && availableLanguages.includes(Settings.data.general.language)) {
+      Logger.d("I18n", `User-defined language found: "${Settings.data.general.language}"`)
+      setLanguage(Settings.data.general.language)
+    } else {
+      Logger.d("I18n", `No user-defined language, using system detected: "${root.systemDetectedLangCode}"`)
+      setLanguage(root.systemDetectedLangCode)
+    }
   }
 
   // -------------------------------------------

Modules/Settings/Tabs/GeneralTab.qml

@@ -204,13 +204,19 @@ ColumnLayout {
       Layout.fillWidth: true
       label: I18n.tr("settings.general.language.select.label")
       description: I18n.tr("settings.general.language.select.description")
-      model: I18n.availableLanguages.map(function(langCode) {
+      model: [
+        { "key": "", "name": I18n.tr("settings.general.language.select.auto-detect") + " (" + I18n.systemDetectedLangCode + ")" }
+      ].concat(I18n.availableLanguages.map(function(langCode) {
         return { "key": langCode, "name": langCode }
-      })
-      currentKey: Settings.data.general.language !== "" ? Settings.data.general.language : I18n.langCode
+      }))
+      currentKey: Settings.data.general.language
       onSelected: key => {
         Settings.data.general.language = key
-        I18n.setLanguage(key)
+        if (key === "") {
+          I18n.detectLanguage() // Re-detect system language if "Automatic" is selected
+        } else {
+          I18n.setLanguage(key) // Set specific language
+        }
       }
     }
   }