🐛 Fix unhandled AbortError in HTTP fetch requests

Identify and silence "signal is aborted without reason" errors by:
- Providing an explicit reason to AbortController when subscriptions are disposed.
- Updating the global error handler to ignore AbortError exceptions.
- Ensuring unhandled rejections use the ignorable exception filter.

The root cause was RxJS disposal calling .abort() without a reason, combined
with the on-unhandled-rejection handler missing the ignorable error filter.

Signed-off-by: Andrey Antukh <niwi@niwi.nz>

frontend/src/app/main/errors.cljs

@@ -343,7 +343,12 @@
                   (= message "Possible side-effect in debug-evaluate")
                   (= message "Unexpected end of input")
                   (str/starts-with? message "invalid props on component")
-                  (str/starts-with? message "Unexpected token "))))
+                  (str/starts-with? message "Unexpected token ")
+                  ;; Abort errors are expected when an in-flight HTTP request is
+                  ;; cancelled (e.g. via RxJS unsubscription / take-until).  They
+                  ;; are handled gracefully inside app.util.http/fetch and must
+                  ;; NOT be surfaced as application errors.
+                  (= (.-name ^js cause) "AbortError"))))
 
           (on-unhandled-error [event]
             (.preventDefault ^js event)

frontend/src/app/util/http.cljs

@@ -123,10 +123,15 @@
                                 (/ current-time (inc count)))
                      count (inc count)]
                  (swap! network-averages assoc (:path uri) {:count count :average average})))))
+
        (fn []
          (vreset! unsubscribed? true)
          (when @abortable?
-           (.abort ^js controller)))))))
+           ;; Provide an explicit reason so that the resulting AbortError carries
+           ;; a meaningful message instead of the browser default
+           ;; "signal is aborted without reason".
+           (.abort ^js controller (ex-info (str "fetch to '" uri "' is aborted")
+                                           {:uri uri}))))))))
 
 (defn response->map
   [response]