Localize Home Assistant environment variable UI text

- Add translation keys for environment-managed labels
- Replace hardcoded English text with i18n function calls
- Add translations for English, German, and Japanese
- Keys: environmentManagedLabel, autoEnabledViaEnv, urlFromEnvReadOnly, tokenFromEnvReadOnly

Addresses PR feedback on #283

frontend/src/i18n/locales/de.ts

@@ -1093,6 +1093,10 @@ export default {
     enableRetry: 'Wiederholung aktivieren',
     // Home Assistant
     homeAssistantDescription: 'Smart Plugs über Home Assistant steuern',
+    environmentManagedLabel: '(Umgebungsvariable)',
+    autoEnabledViaEnv: 'Automatisch über Umgebungsvariablen aktiviert',
+    urlFromEnvReadOnly: 'Wert wird über HA_URL Umgebungsvariable gesetzt (schreibgeschützt)',
+    tokenFromEnvReadOnly: 'Wert wird über HA_TOKEN Umgebungsvariable gesetzt (schreibgeschützt)',
     // MQTT
     mqttConnectedTo: 'Verbunden mit',
     // Prometheus

frontend/src/i18n/locales/en.ts

@@ -1093,6 +1093,10 @@ export default {
     enableRetry: 'Enable retry',
     // Home Assistant
     homeAssistantDescription: 'Control smart plugs via Home Assistant',
+    environmentManagedLabel: '(Environment Managed)',
+    autoEnabledViaEnv: 'Automatically enabled via environment variables',
+    urlFromEnvReadOnly: 'Value set by HA_URL environment variable (read-only)',
+    tokenFromEnvReadOnly: 'Value set by HA_TOKEN environment variable (read-only)',
     // MQTT
     mqttConnectedTo: 'Connected to',
     // Prometheus

frontend/src/i18n/locales/ja.ts

@@ -1274,6 +1274,10 @@ export default {
     connected: '接続済み',
     disconnected: '未接続',
     homeAssistantDescription: 'Home Assistantに接続してHA REST APIでスマートプラグを制御します。switch、light、input_booleanエンティティに対応しています。',
+    environmentManagedLabel: '(環境変数で管理)',
+    autoEnabledViaEnv: '環境変数により自動的に有効化されました',
+    urlFromEnvReadOnly: 'HA_URL環境変数で設定された値（読み取り専用）',
+    tokenFromEnvReadOnly: 'HA_TOKEN環境変数で設定された値（読み取り専用）',
     enableHA: 'Home Assistantを有効化',
     enableHADescription: 'Home Assistantでスマートプラグを制御',
     haUrl: 'Home Assistant URL',

frontend/src/pages/SettingsPage.tsx

@@ -1981,7 +1981,7 @@ export function SettingsPage() {
                     <div className="flex items-center gap-1 mt-1">
                       <Lock className="w-3 h-3 text-bambu-green" />
                       <span className="text-xs text-bambu-green">
-                        Automatically enabled via environment variables
+                        {t('settings.autoEnabledViaEnv')}
                       </span>
                     </div>
                   )}
@@ -2007,7 +2007,7 @@ export function SettingsPage() {
                       Home Assistant URL
                       {localSettings.ha_url_from_env && (
                         <span className="ml-2 text-xs text-bambu-green">
-                          (Environment Managed)
+                          {t('settings.environmentManagedLabel')}
                         </span>
                       )}
                     </label>
@@ -2028,7 +2028,7 @@ export function SettingsPage() {
                     </div>
                     {localSettings.ha_url_from_env && (
                       <p className="text-xs text-bambu-gray mt-1">
-                        Value set by HA_URL environment variable (read-only)
+                        {t('settings.urlFromEnvReadOnly')}
                       </p>
                     )}
                   </div>
@@ -2038,7 +2038,7 @@ export function SettingsPage() {
                       Long-Lived Access Token
                       {localSettings.ha_token_from_env && (
                         <span className="ml-2 text-xs text-bambu-green">
-                          (Environment Managed)
+                          {t('settings.environmentManagedLabel')}
                         </span>
                       )}
                     </label>
@@ -2059,7 +2059,7 @@ export function SettingsPage() {
                     </div>
                     {localSettings.ha_token_from_env ? (
                       <p className="text-xs text-bambu-gray mt-1">
-                        Value set by HA_TOKEN environment variable (read-only)
+                        {t('settings.tokenFromEnvReadOnly')}
                       </p>
                     ) : (
                       <p className="text-xs text-bambu-gray mt-1">