fix: address code review findings for DNS management

- CRITICAL: Change DNS zones endpoint from GET to POST to avoid
  leaking API token in URL query parameters
- HIGH: Add sync.RWMutex to protect dnsProvider field in Server,
  Deployer, and proxy Manager against concurrent read/write races
- HIGH: Capture old DNS provider reference synchronously before
  launching background cleanup goroutine
- HIGH: Use getDNS()/getDNSProviderLocked() accessors instead of
  direct field reads in all DNS operations

web/.svelte-kit/output/server/chunks/Skeleton.js

@@ -0,0 +1,13 @@
+import { b as attr_class, l as attr_style, g as stringify } from "./index.js";
+function Skeleton($$renderer, $$props) {
+  const {
+    class: className = "",
+    width = "100%",
+    height = "1rem",
+    rounded = false
+  } = $$props;
+  $$renderer.push(`<div${attr_class(`skeleton ${stringify(className)}`)}${attr_style(`width: ${stringify(width)}; height: ${stringify(height)}; ${stringify(rounded ? "border-radius: 9999px;" : "")}`)} aria-hidden="true"></div>`);
+}
+export {
+  Skeleton as S
+};