fix(toast): show success toast for HTMX JSON responses

Previously, when HTMX form submissions (profile update, password change)
returned a successful JSON response like {"message": "profile updated
successfully"}, the raw JSON was swapped into the target div as plain text.

The htmx:afterSwap listener in toast.ts only handled error responses.
Extend it to also intercept successful 2xx JSON responses that contain a
"message" field, showing a green success toast and clearing the raw JSON
from the target element. Only JSON responses are intercepted (checked via
Content-Type header), so legitimate HTML swaps are unaffected.

web/src/toast.ts

@@ -138,14 +138,31 @@ const setupHTMXListeners = (): void => {
 
     const customEvent = evt as CustomEvent<HTMXEventDetail>;
 
-    // Check if request failed
-    if (customEvent.detail.succeeded === false && customEvent.detail.xhr) {
+    if (customEvent.detail.xhr) {
       const xhr = customEvent.detail.xhr;
 
-      // Show toast for HTTP errors
-      if (xhr.status >= 400 && xhr.status < 600) {
+      if (
+        customEvent.detail.succeeded === false &&
+        xhr.status >= 400 &&
+        xhr.status < 600
+      ) {
         const errorMessage = parseXHRError(xhr);
         showToast(errorMessage, "error");
+      } else if (xhr.status >= 200 && xhr.status < 300) {
+        const contentType = xhr.getResponseHeader("content-type");
+        if (contentType && contentType.includes("application/json")) {
+          try {
+            const response = JSON.parse(xhr.responseText);
+            if (response.message) {
+              showToast(response.message, "success");
+              if (customEvent.detail.target) {
+                customEvent.detail.target.innerHTML = "";
+              }
+            }
+          } catch (e) {
+            // Not valid JSON — ignore
+          }
+        }
       }
     }
   });