Add post_progress_to_api lightweight telemetry ping

Introduce post_progress_to_api() in misc/api.func — a non-blocking, fire-and-forget curl ping (gated by DIAGNOSTICS and RANDOM_UUID) that updates telemetry status to "configuring". Wire this progress ping into multiple scripts (alpine-install.func, install.func, build.func, core.func) at key milestones (container start, network ready, customization, creation, cleanup) and replace/deduplicate some earlier post_to_api calls. Also update error_handler.func to always report failures immediately via post_update_to_api to ensure failures are captured even before/after container lifecycle.

misc/core.func

@@ -1496,6 +1496,11 @@ cleanup_lxc() {
   fi
 
   msg_ok "Cleaned"
+  
+  # Send progress ping if available (defined in install.func)
+  if declare -f post_progress_to_api &>/dev/null; then
+    post_progress_to_api
+  fi
 }
 
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