feat(songs): implement .pro file upload in SongDB page

- Replace placeholder exception with real uploadProFiles() function
- POST files to /api/songs/import-pro endpoint
- Show success/error toast and refresh song list after import

resources/js/Pages/Songs/Index.vue

@@ -2,6 +2,7 @@
 import AuthenticatedLayout from '@/Layouts/AuthenticatedLayout.vue'
 import SongEditModal from '@/Components/SongEditModal.vue'
 import { Head } from '@inertiajs/vue3'
+import axios from 'axios'
 import { ref, watch, onMounted } from 'vue'
 
 const songs = ref([])
@@ -139,11 +140,12 @@ function handleDragLeave() {
     isDragging.value = false
 }
 
-function handleDrop(e) {
+async function handleDrop(e) {
     e.preventDefault()
     isDragging.value = false
-    uploadError.value = 'ProPresenter-Import (.pro) ist noch nicht verfügbar. Kommt bald!'
-    setTimeout(() => { uploadError.value = '' }, 4000)
+    const droppedFiles = Array.from(e.dataTransfer?.files || [])
+    if (droppedFiles.length === 0) return
+    await uploadProFiles(droppedFiles)
 }
 
 function triggerFileInput() {
@@ -151,9 +153,42 @@ function triggerFileInput() {
 }
 
 function handleFileSelect() {
-    uploadError.value = 'ProPresenter-Import (.pro) ist noch nicht verfügbar. Kommt bald!'
+    const selectedFiles = Array.from(fileInput.value?.files || [])
     if (fileInput.value) fileInput.value.value = ''
-    setTimeout(() => { uploadError.value = '' }, 4000)
+    if (selectedFiles.length === 0) return
+    uploadProFiles(selectedFiles)
+}
+
+async function uploadProFiles(files) {
+    uploadError.value = ''
+    loading.value = true
+    let successCount = 0
+    let errors = []
+
+    for (const file of files) {
+        const formData = new FormData()
+        formData.append('file', file)
+
+        try {
+            await axios.post('/api/songs/import-pro', formData, {
+                headers: { 'Content-Type': 'multipart/form-data' },
+            })
+            successCount++
+        } catch (err) {
+            const message = err.response?.data?.message || `Fehler bei "${file.name}"`
+            errors.push(message)
+        }
+    }
+
+    if (successCount > 0) {
+        await fetchSongs(1)
+    }
+
+    if (errors.length > 0) {
+        uploadError.value = errors.join(', ')
+        setTimeout(() => { uploadError.value = '' }, 6000)
+    }
+    loading.value = false
 }
 
 // Page range for pagination