feat(translate): add translation presets and custom instructions

src/qml/TranslationSettings.qml

@@ -145,6 +145,51 @@ SettingsBasePage {
                 onEditingFinished: QtPotatoSettings.save()
             }
 
+            Label {
+                text: KI18n.i18nc("@label:listbox", "Preset")
+                Layout.alignment: Qt.AlignRight | Qt.AlignTop
+            }
+
+            ColumnLayout {
+                Layout.fillWidth: true
+
+                ComboBox {
+                    id: presetCombo
+                    Layout.fillWidth: true
+                    model: root.translator.translationPresets
+                    textRole: "name"
+                    valueRole: "id"
+                    Component.onCompleted: currentIndex = Math.max(0, indexOfValue(QtPotatoSettings.translationPreset))
+                    onActivated: {
+                        QtPotatoSettings.translationPreset = currentValue
+                        QtPotatoSettings.save()
+                    }
+                }
+
+                Label {
+                    text: presetCombo.currentIndex >= 0 ? presetCombo.model[presetCombo.currentIndex].guidance : ""
+                    wrapMode: Text.WordWrap
+                    opacity: 0.7
+                    Layout.fillWidth: true
+                }
+            }
+
+            Label {
+                text: KI18n.i18nc("@label:textbox", "Additional instructions")
+                Layout.alignment: Qt.AlignRight | Qt.AlignTop
+            }
+
+            TextArea {
+                text: QtPotatoSettings.customInstructions
+                placeholderText: KI18n.i18nc("@info:placeholder", "e.g. Translate 'Young Master' as 'Thiếu gia'. Use 'ta/ngươi' between enemies.")
+                wrapMode: TextArea.Wrap
+                Layout.fillWidth: true
+                Layout.preferredHeight: Kirigami.Units.gridUnit * 4
+                // TextArea has no textEdited before Qt 6.9.
+                onTextChanged: QtPotatoSettings.customInstructions = text
+                onEditingFinished: QtPotatoSettings.save()
+            }
+
             Label {
                 text: KI18n.i18nc("@label:spinbox", "Lines per request")
                 Layout.alignment: Qt.AlignRight