stop automatic SWR image reloading

Disable periodic and station-status-triggered SWR report refreshes on the web UI, and only use per-band updatedAt values for cache-busting image URLs. This prevents constant image refetching while still loading new images when their timestamps actually change.

public/app.js

@@ -293,7 +293,6 @@ async function init() {
     const route = currentRoute();
     if (route === "/rms/swr" || route === "/rms") {
       refreshStatus().catch(() => {});
-      refreshSwrReport().catch(() => {});
     }
   }, SWR_DETAIL_REFRESH_MS);
 }
@@ -2215,7 +2214,7 @@ function renderSwrBandsInto(container, report, options = {}) {
 
   container.classList.remove("swr-summary-list");
   for (const band of bands) {
-    const imageVersion = band.updatedAt || report.generatedAt || "";
+    const imageVersion = band.updatedAt || "";
     const imageUrl = withCacheVersion(band.imageUrl, imageVersion);
     const block = document.createElement("div");
     block.className = "plugin-block";
@@ -4687,7 +4686,6 @@ function connectEvents() {
   };
   eventSource.addEventListener("station.status.changed", async () => {
     await refreshStatus();
-    await refreshSwrReport();
     if (canSeeActivityLog()) {
       await refreshActivityLog();
     }
@@ -4748,7 +4746,7 @@ function connectEvents() {
     await refreshStatus();
   });
   eventSource.addEventListener("swr.report.changed", async () => {
-    await refreshSwrReport();
+    // SWR images are intentionally not auto-reloaded to avoid repeated browser fetches.
   });
   eventSource.addEventListener("plugin.provider.changed", async () => {
     await refreshPlugins();