feat: improve error handling and logging in the web application

- Updated the error handling in `index.html` to include a retry button for failed app loads, enhancing user experience.
- Added session storage management to prevent repeated reloads on errors.
- Enhanced the `.gitignore` file to include log files, improving project cleanliness.
- Included error logging in `main.js` to ensure better tracking of issues during app initialization.

.gitignore

@@ -14,3 +14,6 @@ htmlcov/
 .pytest_cache/
 *.cover
 *.plan.md
+
+# Logs
+*.log

webapp/index.html

@@ -73,14 +73,30 @@
       var mainScript = document.getElementById("main-module");
       if (mainScript) {
         mainScript.addEventListener("error", function() {
+          var retryKey = "__dtLoadRetry";
+          try {
+            if (!sessionStorage.getItem(retryKey)) {
+              sessionStorage.setItem(retryKey, "1");
+              location.reload();
+              return;
+            }
+            sessionStorage.removeItem(retryKey);
+          } catch (_) {}
           var loading = document.getElementById("loading");
           if (loading && !loading.classList.contains("hidden")) {
             loading.classList.add("hidden");
-            var err = document.getElementById("error");
-            if (err) {
-              err.hidden = false;
-              err.textContent = "Failed to load app. Check connection and try again.";
-            }
+          }
+          var err = document.getElementById("error");
+          if (err) {
+            err.hidden = false;
+            err.textContent = "";
+            err.appendChild(document.createTextNode("Failed to load app. Check connection and try again. "));
+            var retryBtn = document.createElement("button");
+            retryBtn.type = "button";
+            retryBtn.className = "error-retry";
+            retryBtn.textContent = "Retry";
+            retryBtn.addEventListener("click", function() { location.reload(); });
+            err.appendChild(retryBtn);
           }
         });
       }

webapp/js/main.js

@@ -68,6 +68,9 @@ applyLangToUi();
 
 logger.info("App init", "lang=" + state.lang);
 
+try {
+  sessionStorage.removeItem("__dtLoadRetry");
+} catch (_) {}
 window.__dtReady = true;
 
 /**