feat(python): catch all exceptions thrown through fastapi route paths

This commit does quite a bit:
- Catches unhandled exceptions raised in the route handler and
  produces a 500 Internal Server Error Arch-themed response.
- Each unhandled exception causes a notification to be sent to new
  `notifications.postmaster` email with a "Traceback ID."
- Traceback ID is logged to the server along with the traceback which
  caused the 500: `docker-compose logs fastapi | grep '<traceback_id>'`
- If `options.traceback` is set to `1`, traceback is displayed in
  the new 500.html template.

Signed-off-by: Kevin Morris <kevr@0cost.org>

web/html/css/aurweb.css

@@ -255,3 +255,12 @@ div.box form.link p {
 div.box form.link button {
     padding: 0;
 }
+
+pre.traceback {
+    /* https://css-tricks.com/snippets/css/make-pre-text-wrap/ */
+    white-space: pre-wrap;
+    white-space: -moz-pre-wrap;
+    white-space: -pre-wrap;
+    white-space: -o-pre-wrap;
+    word-wrap: break-all;
+}