ui: Request higher video resolution from camera

Apparently, you get 640x480 unless you ask for more?  Need to constrain
the viewer size, though, otherwise it massively overflows the page and
makes it impossible to see what you're taking a picture of.

js/transaction.css

@@ -6,6 +6,13 @@
   text-align: center;
 }
 
+#photo-view video,
+#photo-view canvas {
+  width: 100%;
+  height: auto;
+  object-fit: contain;
+}
+
 #photo-view sl-icon-button {
   font-size: 3em;
   margin: 0 0.5em;

js/transaction.ts

@@ -50,6 +50,8 @@ async function startCamera() {
                 facingMode: {
                     ideal: "environment",
                 },
+                width: { ideal: 1280 },
+                height: { ideal: 720 },
             },
             audio: false,
         });