feat: add PDF import support and improve OCR chord parsing and translation

src/app/pages/propose-canto/propose-canto.page.html

@@ -16,8 +16,8 @@
 
   <div class="drag-overlay" *ngIf="isDraggingOver">
     <div class="drag-message">
-      <ion-icon name="image-outline"></ion-icon>
-      <p>Rilascia l'immagine qui per estrarre il testo</p>
+      <ion-icon name="document-text-outline"></ion-icon>
+      <p>Rilascia l'immagine o il PDF qui per estrarre il testo</p>
     </div>
   </div>
 
@@ -109,6 +109,9 @@
                 <ion-button fill="clear" size="small" (click)="takePhoto()">
                   <ion-icon name="camera-outline"></ion-icon>
                 </ion-button>
+                <ion-button fill="clear" size="small" (click)="chooseFile()">
+                  <ion-icon name="document-attach-outline"></ion-icon>
+                </ion-button>
               </div>
             </div>
             <ion-item class="custom-input-item textarea-item">
@@ -191,4 +194,5 @@
 
   <!-- Hidden inputs -->
   <input type="file" #cameraInput (change)="onFileSelected($event, true)" accept="image/*" capture="camera" style="display: none;">
+  <input type="file" #fileInput (change)="onFileSelected($event, false)" accept="image/*,application/pdf" style="display: none;">
 </ion-content>