feat: add product interaction mode selector with three scenarios

- Add ItemToggleButton component for 3-way toggle in admin panel
- Add product_interaction_mode setting with options: order, manager, browser
- Add manager_username setting for Telegram manager contact
- Remove store_enabled setting, replaced with product_interaction_mode
- Create migration to automatically migrate store_enabled to product_interaction_mode
- Update Product.vue to handle all three interaction modes
- Update Dock.vue to show cart button only when product_interaction_mode is 'order'
- Rename 'Магазин' tab to 'Витрина' in admin panel
- Remove 'Разрешить покупки' option (now controlled via product_interaction_mode)
- Set default product_interaction_mode to 'browser'
- Update StoreDTO to remove enableStore field
- Update SettingsHandler to return product_interaction_mode instead of store_enabled

frontend/admin/src/components/Settings/ItemToggleButton.vue

@@ -0,0 +1,51 @@
+<template>
+  <SettingsItem :label="label">
+    <template #default>
+      <SelectButton
+        :modelValue="model"
+        :options="options"
+        optionLabel="label"
+        optionValue="value"
+        :allowEmpty="false"
+        @update:modelValue="updateValue"
+      />
+    </template>
+    <template #help>
+      <slot/>
+    </template>
+  </SettingsItem>
+</template>
+
+<script setup>
+import {computed} from "vue";
+import SettingsItem from "@/components/SettingsItem.vue";
+import SelectButton from "primevue/selectbutton";
+
+const model = defineModel();
+const props = defineProps({
+  items: {
+    type: Object,
+    default: {},
+  },
+  label: {
+    type: String,
+    default: '',
+  },
+});
+
+const options = computed(() => {
+  return Object.entries(props.items).map(([value, label]) => ({
+    value,
+    label,
+  }));
+});
+
+function updateValue(newValue) {
+  model.value = newValue;
+}
+</script>
+
+<style scoped>
+
+</style>
+