refactor(lua)!: migrate to the per-feature namespaces

Follows lib/esp32-lua-api: gui -> screen, node -> tree, settings and input
split into screen/sys/touch/buttons. Settings is one provider lighter, with
timezone on Sys and rotation and theme on Gui, which now applies and persists a
rotation in one call. The calibration screen stashes the rotation it borrows
rather than relying on a transient setter.

src/main.cpp

@@ -1,7 +1,3 @@
-// Board bring-up and the loop. Everything about running a Lua app -- the state,
-// the bindings, app loading, navigation history -- lives in the shared runtime
-// behind LuaHost.
-
 #include <SD.h>
 #include <SPI.h>
 #include <TFT_eSPI.h>
@@ -31,10 +27,10 @@ LuaHost host(tft, touch);
 static bool halted = false;
 
 static void fallbackScreen(const char* message) {
-  tft.resetViewport(); // no app, no status bar: this message owns the panel
+  tft.resetViewport();
   tft.setRotation(0);
   tft.fillScreen(TFT_WHITE);
-  tft.setTextSize(2);
+  tft.setTextSize(1);
   tft.setTextColor(TFT_RED, TFT_WHITE);
   tft.drawString(message, 10, 10);
   tft.setTextColor(TFT_BLACK, TFT_WHITE);
@@ -43,7 +39,7 @@ static void fallbackScreen(const char* message) {
   halted = true;
 }
 
-// ponytail: fixed 10s / 8% dim, no fade. Make it a setting when someone asks.
+// Auto Dim
 constexpr uint32_t kDimAfterMs = 10000;
 constexpr int kBacklightChannel = 0;
 uint32_t lastTouchMs = 0;
@@ -62,8 +58,7 @@ void updateBacklight() {
 void setup() {
   Serial.begin(115200);
 
-  // A failed new otherwise unwinds to terminate() and a bare abort backtrace.
-  // Nothing can be freed at that point, so this only buys a legible cause.
+  // OOM Logging
   std::set_new_handler([]() {
     logHeap("oom");
     Serial.println("[fatal] out of memory");
@@ -71,41 +66,52 @@ void setup() {
     ESP.restart();
   });
 
+  // Start TFT
   tft.begin();
   tft.setRotation(0);
   tft.fillScreen(TFT_WHITE);
   touchSpi.begin(14, 12, 13, TOUCH_CS);
   touch.begin(touchSpi);
 
-  // TFT_eSPI leaves TFT_BL a plain output; LEDC takes it over for dimming.
+  // TFT Dimming
   ledcSetup(kBacklightChannel, 5000, 8);
   ledcAttachPin(TFT_BL, kBacklightChannel);
   ledcWrite(kBacklightChannel, 255);
   lastTouchMs = millis();
 
+  // SD Card
   sdSpi.begin(SD_SCK, SD_MISO, SD_MOSI, SD_CS);
   if (!SD.begin(SD_CS, sdSpi)) {
     fallbackScreen("SD card mount failed");
     return;
   }
 
-  settings.load(); // absent file keeps the built-in defaults
+  // Load Settings & Load Lua
+  settings.load();
   net::begin();
   if (!host.begin())
     fallbackScreen("home failed to start");
+
+  // Start WiFi
   net::startWifi();
 }
 
 void loop() {
+  // Halted
   if (halted) {
     delay(100);
     return;
   }
+
+  // Auto Dim & Net / Lua Loop
   updateBacklight();
   net::loop();
   host.loop();
-  // The launcher failing to start is the one error no app can recover from.
+
+  // Failed Lua Main
   if (!host.running())
     fallbackScreen("home failed to start");
+
+  // Yield
   delay(1);
 }