Weather info popup, larger System menu buttons, group Flight toggles

Tapping the weather icon in the header now shows a small info popup
explaining that the shown weather always follows the currently active
location (including an active location preset).

The System menu's buttons now fill the available screen height
instead of leaving unused space below, computed from a dedicated
systemRowRect() helper. "Info" (About) is pinned as the second-to-last
entry, directly above Back, so its position stays stable regardless of
how many other entries come before it.

In the Flight options menu, all plain ON/OFF toggles (LED heartbeat,
emergency alert, proximity LED, watchlist alert, hide ground vehicles)
are now grouped together at the end of the list, right above Back,
instead of being interleaved with the screen/list entries above them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/i18n_en.h

@@ -201,6 +201,9 @@ static const char* const I18N_EN[] = {
     "Logbook / WebUI",
     "This web page lets you view, download and individually delete the flight logbook right from a browser. While connected to the same WiFi network, open a browser and go to:",
     "No WiFi connection - the page is only reachable while connected to a network.",
+
+    "Weather",
+    "The weather icon shows the current weather for your active location. If a location preset is selected, its weather is shown instead.",
 };
 
 static_assert(sizeof(I18N_EN) / sizeof(I18N_EN[0]) == (size_t)StringId::COUNT,