fix(deploy): redeploy button after save, disable save when clean, success toast

- Bug 1: default serverDirtyAgainstDeploy to true (not false) while
  dirtyState query is loading — prevents the button showing 'Save'
  instead of 'Redeploy' on apps with no successful deployment yet.
- Bug 2: normalize samplingRate from server as '<n>.0' when the value
  is a whole-number float so serverState matches form after save,
  eliminating spurious dirty detection that kept Save enabled.
- Bug 3: add success toast after handleSave completes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/pages/AppsTab/AppDeploymentPage/index.tsx

@@ -113,7 +113,7 @@ export default function AppDeploymentPage() {
   const dirty = useFormDirty(form, serverState, stagedJar);
   const { dialogOpen: blockerOpen, confirm: blockerConfirm, cancel: blockerCancel } =
     useUnsavedChangesBlocker(dirty.anyLocalEdit);
-  const serverDirtyAgainstDeploy = dirtyState?.dirty ?? false;
+  const serverDirtyAgainstDeploy = dirtyState?.dirty ?? true;
   const deploymentInProgress = !!activeDeployment;
   const primaryMode = computeMode({
     deploymentInProgress,
@@ -220,6 +220,8 @@ export default function AppDeploymentPage() {
 
       setStagedJar(null);
 
+      toast({ title: 'Configuration saved', variant: 'success' });
+
       // Invalidate dirty-state so the button reflects the new saved state
       await queryClient.invalidateQueries({ queryKey: ['apps', envSlug, targetApp.slug, 'dirty-state'] });