fix(web): wait for async plugin install to finish before auto-enabling it

Confirmed live: installing hockey-scoreboard logged "installation queued"
(success) immediately followed by "enabling it failed" with a 404 "Plugin
not found" from /api/v3/plugins/toggle.

/api/v3/plugins/install runs the actual clone + plugin-manager discovery
asynchronously via an operation queue when one is configured - the response
installPlugin() was checking only means the operation was queued, not that
the plugin is installed yet. Calling togglePlugin() right after that
response 404s because plugin_manager hasn't discovered the new plugin.

Fix: reuse the same operation-polling mechanism uninstallPlugin() already
has (generalized pollOperationStatus() to take onComplete/onFailed/onTimeout
callbacks instead of hardcoding uninstall behavior) so installPlugin() waits
for the operation to actually complete before enabling it. Falls back to
enabling immediately when no operation_id is returned (direct/synchronous
install path, no queue configured).

web_interface/static/v3/plugins_manager.js

@@ -3334,16 +3334,28 @@ window.uninstallPlugin = function(pluginId) {
     });
 }
 
-function pollOperationStatus(operationId, pluginId, pluginName, maxAttempts = 60, attempt = 0) {
+function pollOperationStatus(operationId, pluginId, pluginName, options = {}) {
+    const maxAttempts = options.maxAttempts || 60;
+    const attempt = options.attempt || 0;
+    const onComplete = options.onComplete || (() => handleUninstallSuccess(pluginId));
+    const onFailed = options.onFailed || ((errorMsg) => {
+        showNotification(errorMsg || `Operation failed for ${pluginName}`, 'error');
+        setTimeout(() => loadInstalledPlugins(), 1000);
+    });
+    const onTimeout = options.onTimeout || (() => {
+        showNotification(`Operation timed out for ${pluginName}`, 'error');
+        setTimeout(() => loadInstalledPlugins(), 1000);
+    });
+
     if (attempt >= maxAttempts) {
-        showNotification(`Uninstall operation timed out for ${pluginName}`, 'error');
+        onTimeout();
-        // Refresh plugin list to see actual state
-        setTimeout(() => {
-            loadInstalledPlugins();
-        }, 1000);
         return;
     }
 
+    const pollAgain = () => setTimeout(() => {
+        pollOperationStatus(operationId, pluginId, pluginName, { ...options, attempt: attempt + 1 });
+    }, 1000);
+
     fetch(`/api/v3/plugins/operation/${operationId}`)
         .then(response => response.json())
         .then(data => {
@@ -3352,32 +3364,16 @@ function pollOperationStatus(operationId, pluginId, pluginName, maxAttempts = 60
                 const status = operation.status;
 
                 if (status === 'completed') {
-                    // Operation completed successfully
+                    onComplete();
-                    handleUninstallSuccess(pluginId);
                 } else if (status === 'failed') {
-                    // Operation failed
+                    onFailed(operation.error || operation.message);
-                    const errorMsg = operation.error || operation.message || `Failed to uninstall ${pluginName}`;
-                    showNotification(errorMsg, 'error');
-                    // Refresh plugin list to see actual state
-                    setTimeout(() => {
-                        loadInstalledPlugins();
-                    }, 1000);
-                } else if (status === 'pending' || status === 'in_progress') {
-                    // Still in progress, poll again
-                    setTimeout(() => {
-                        pollOperationStatus(operationId, pluginId, pluginName, maxAttempts, attempt + 1);
-                    }, 1000); // Poll every second
                 } else {
-                    // Unknown status, poll again
+                    // 'pending', 'in_progress', or unknown - poll again
-                    setTimeout(() => {
+                    pollAgain();
-                        pollOperationStatus(operationId, pluginId, pluginName, maxAttempts, attempt + 1);
-                    }, 1000);
                 }
             } else {
                 // Error getting operation status, try again
-                setTimeout(() => {
+                pollAgain();
-                    pollOperationStatus(operationId, pluginId, pluginName, maxAttempts, attempt + 1);
-                }, 1000);
             }
         })
         .catch(error => {
@@ -3883,15 +3879,7 @@ window.installPlugin = function(pluginId, branch = null) {
         requestBody.branch = branch;
     }
 
-    fetch('/api/v3/plugins/install', {
+    function enableAfterInstall() {
-        method: 'POST',
-        headers: { 'Content-Type': 'application/json' },
-        body: JSON.stringify(requestBody)
-    })
-    .then(response => response.json())
-    .then(data => {
-        showNotification(data.message, data.status);
-        if (data.status === 'success') {
         // Enable immediately so install -> enable is one step; only nudge
         // for a restart once enablement actually succeeded (persistent
         // toast; duration 0 = stays until dismissed).
@@ -3917,6 +3905,33 @@ window.installPlugin = function(pluginId, branch = null) {
         loadInstalledPlugins();
         setTimeout(() => applyStoreFiltersAndSort(true), 500);
     }
+
+    fetch('/api/v3/plugins/install', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify(requestBody)
+    })
+    .then(response => response.json())
+    .then(data => {
+        showNotification(data.message, data.status);
+        if (data.status !== 'success') return;
+
+        if (data.data && data.data.operation_id) {
+            // Install runs async via the operation queue - this response only
+            // means "queued", not "installed". Enabling immediately here would
+            // 404 with "Plugin not found" against the toggle endpoint, since
+            // the plugin manager hasn't discovered the new plugin yet (seen
+            // live: "installation queued" followed immediately by a failed
+            // enable). Wait for the operation to actually finish first.
+            pollOperationStatus(data.data.operation_id, pluginId, pluginId, {
+                onComplete: enableAfterInstall,
+                onFailed: (errorMsg) => showNotification(errorMsg || `Failed to install ${pluginId}`, 'error'),
+                onTimeout: () => showNotification(`Install operation timed out for ${pluginId}`, 'error')
+            });
+        } else {
+            // No operation queue configured - install already completed synchronously.
+            enableAfterInstall();
+        }
     })
     .catch(error => {
         showNotification('Error installing plugin: ' + error.message, 'error');