perf: increase render interval on static screens from 300ms to 2000ms

Static screens (SettingsScreen, BotScreen, FullscreenMsgView, message
list, contact picker) were re-rendering every 300ms with no visible
benefit. New messages still trigger immediate refresh via newMsg() →
_next_refresh=100, so responsiveness is unchanged. Reduces unnecessary
SPI transfers and CPU wakeups ~6x on idle static screens.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/ui-new/BotScreen.h

@@ -97,7 +97,7 @@ public:
       }
       display.setColor(DisplayDriver::LIGHT);
     }
-    return 300;
+    return 2000;
   }
 
   bool handleInput(char c) override {

examples/companion_radio/ui-new/FullscreenMsgView.h

@@ -85,7 +85,7 @@ struct FullscreenMsgView {
       display.setCursor(display.width() - 6, nav_y);
       display.print(">");
     }
-    return 300;
+    return 2000;
   }
 
   Result handleInput(char c) {

examples/companion_radio/ui-new/UITask.cpp

@@ -479,7 +479,7 @@ public:
       display.print("v");
     }
 
-    return 300;
+    return 2000;
   }
 
   bool handleInput(char c) override {
@@ -1298,7 +1298,7 @@ public:
                             _hist_sel < fs_hist_count - 1,
                             _hist_sel > 0);
         }
-        return 300;
+        return 2000;
       }
 
       ChannelDetails ch;
@@ -1426,7 +1426,7 @@ public:
       display.setColor(DisplayDriver::LIGHT);
       renderScrollHints(display, _msg_scroll, total_msg_items);
     }
-    return 300;
+    return 2000;
   }
 
   bool handleInput(char c) override {