fix: recover deployed image from registry on local miss

Adds an app-aware `fn-verify-app-image` helper that pulls the deployed image
from the configured registry when it is missing locally, gated on
push-on-release being enabled, honoring per-app `registry:login` credentials.
Every in-tree `verify_image` caller migrates to the wrapper and the bare
helper is marked deprecated. `config:set` now forwards the deployed image tag
to `release-and-deploy` so the release path no longer pins recovery on the
unrecoverable `:latest` tag.

plugins/git/internal-functions

@@ -176,7 +176,7 @@ cmd-git-load-image() {
   dokku_setup_build_capture "$APP" "git:load-image"
   cat | docker load
 
-  if ! verify_image "$DOCKER_IMAGE"; then
+  if ! fn-verify-app-image "$APP" "$DOCKER_IMAGE"; then
     dokku_log_fail "Loaded image tarball but the specified docker image was not found: $DOCKER_IMAGE"
   fi