ui: improve manual model load and cancel (#847)

- When a model is manually loaded show a cancel buttton and a queued
status
- Implement cancellation in scheduler.Scheduler interface and FIFO
scheduler
- Add cache bust query parameter to bypass browser cache

Fixes #844

ui-svelte/src/index.css

@@ -139,7 +139,8 @@
   }
 
   .status--starting,
-  .status--stopping {
+  .status--stopping,
+  .status--queued {
     @apply bg-warning/10 text-warning;
   }