Moved to uv from poetry

Updated ruff and mypy, accepted all changes
Central exception management and injected the Session.
This removed a lot of duplicated boilerplate code.
Added health check
Updated to Angular 21

overlord/src/app/purchase/purchase.component.html

@@ -179,7 +179,7 @@
   <div class="row-container">
     @for (item of voucher.files; track item) {
       <div class="img-container" class="flex-auto basis-1-5">
-        <img [src]="item.thumbnail" (click)="zoomImage(item)" />
+        <img [src]="item.thumbnail" alt="img" (click)="zoomImage(item)" (keyup.enter)="zoomImage(item)" tabindex="0" />
         <button mat-icon-button class="overlay" (click)="deleteImage(item)">
           <mat-icon>delete</mat-icon>
         </button>
@@ -188,6 +188,7 @@
     <div class="img-container" class="flex flex-auto basis-1-5">
       <label ng-href for="fileUp">
         <img
+          alt="add"
           src="data:image/svg+xml;base64,PHN2ZyB4bWxucz0iaHR0cDovL3d3dy53My5vcmcvMjAwMC9zdmciIHdpZHRoPSIxMDAiIGhlaWdodD0iMTUwIj48cmVjdCB3aWR0aD0iMTAwIiBoZWlnaHQ9IjE1MCIgZmlsbD0iI2VlZSIvPjx0ZXh0IHRleHQtYW5jaG9yPSJtaWRkbGUiIHg9IjUwIiB5PSI3NSIgc3R5bGU9ImZpbGw6I2FhYTtmb250LXdlaWdodDpib2xkO2ZvbnQtc2l6ZToxMDBweDtmb250LWZhbWlseTpBcmlhbCxIZWx2ZXRpY2Esc2Fucy1zZXJpZjtkb21pbmFudC1iYXNlbGluZTpjZW50cmFsIj4rPC90ZXh0Pjwvc3ZnPg=="
         />
       </label>