Fix Home button no-op via native window.load_url() instead of location.href

Reproduced directly: a page loaded over http(s) cannot script-navigate
itself to a file:// URL — the browser silently blocks it (no exception,
no navigation), which is exactly what made the toolbar's Home button do
nothing on a real site. Route it through a new Api.go_home() method
(same pywebview.api pattern already used by Calibrate/Validate/Start
Session) that calls window.load_url(LANDING_URL) natively, bypassing
the page-script navigation restriction entirely.

browser_session.py

@@ -862,9 +862,6 @@ __THEME_CSS__
   document.getElementById('__iux_back').addEventListener('click', function(){ history.back(); });
   document.getElementById('__iux_fwd').addEventListener('click', function(){ history.forward(); });
   document.getElementById('__iux_reload').addEventListener('click', function(){ location.reload(); });
-  document.getElementById('__iux_home').addEventListener('click', function(){
-    location.href = __INSIGHTUX_LANDING_URL__;
-  });
 
   // -- sidebar actions (Python decides validity — camera/session conflicts,
   // wrong page — and reports back through the status text) --
@@ -873,6 +870,11 @@ __THEME_CSS__
       window.pywebview.api[method]();
     }
   }
+  // A page loaded over http(s) can't script-navigate itself to a file://
+  // URL — the browser silently blocks it, no exception, no navigation —
+  // so this has to go through the native window.load_url() call in
+  // Api.go_home() instead of a plain location.href assignment.
+  document.getElementById('__iux_home').addEventListener('click', function(){ callApi('go_home'); });
   document.getElementById('__iux_calibrate').addEventListener('click', function(){ callApi('start_calibration'); });
   document.getElementById('__iux_validate').addEventListener('click', function(){ callApi('run_validation'); });
   document.getElementById('__iux_session').addEventListener('click', function(){ callApi('toggle_session'); });
@@ -941,7 +943,6 @@ __THEME_CSS__
   }, true);  // capture phase — fires before page scripts can intercept/stop the event
 })();
 """
-CHROME_JS = CHROME_JS.replace("__INSIGHTUX_LANDING_URL__", json.dumps(LANDING_URL))
 CHROME_JS = CHROME_JS.replace("__ICONS_JS__", theme.ICONS_JS)
 CHROME_JS = CHROME_JS.replace("__THEME_JS__", theme.THEME_TOGGLE_JS)
 CHROME_JS = CHROME_JS.replace("__THEME_CSS__", theme.THEME_CSS)
@@ -1838,6 +1839,20 @@ class Api:
         print("[browser_session] quit_app() called from JS -- terminating process")
         os._exit(0)
 
+    def go_home(self):
+        # A page loaded over http(s) can't script-navigate itself to a
+        # file:// URL — Chromium/WebView2 silently blocks it (no exception,
+        # no navigation), which is what made the toolbar's Home button a
+        # no-op via location.href. window.load_url() is a native host call,
+        # not page script, so it isn't subject to that restriction — same
+        # mechanism the report page's own navigation already relies on.
+        print("[browser_session] go_home() called from JS")
+        try:
+            self.window.load_url(LANDING_URL)
+        except Exception as e:
+            print(f"[browser_session] go_home failed: {e}")
+        return True
+
     # -- calibration / validation ------------------------------------------
     # calibrate.py and validate.py are unmodified, standalone OpenCV/pyautogui
     # scripts (their own fullscreen window, their own event loop) — they were