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.h

@@ -214,6 +214,13 @@ enum class StringId : uint8_t {
     WEBUI_INFO_PARA1,
     WEBUI_INFO_PARA2,
 
+    // Kleines Info-Fenster, das beim Antippen des Wetter-Icons im Header
+    // erscheint (siehe main.cpp/showWeatherInfo()) - erklaert, dass das
+    // Wetter zum aktuell aktiven Standort (bzw. aktivem Standort-Preset)
+    // gehoert.
+    WEATHER_INFO_TITLE,
+    WEATHER_INFO_BODY,
+
     COUNT
 };