refactor(api)!: one namespace per feature, screen split out

Namespaces were shared across features: `settings` was written by core, the
panel and touch, and `input` by touch and buttons. That made "does this
firmware implement the whole feature?" a question no pointer could answer.

Each namespace now belongs to exactly one feature or to core, so a feature is
a provider pointer and the compiler validates completeness:

  gui, node       -> screen, tree, under the screen feature
  settings        -> screen (rotation, theme), sys (timezone),
                     touch (calibration)
  input           -> touch, buttons

Runtime::open() no longer requires a GuiProvider; a firmware without one runs
with no screen/tree globals and reports sys.hasFeature("screen") false.
Rotation is one value again: GuiProvider::setRotation applies and persists, so
an app rotating the panel transiently puts the old value back itself.

native/include/lua/runtime.h

@@ -25,15 +25,14 @@ constexpr const char* MAIN_PATH = "/.lua/main.lua";
 // registered.
 struct Providers {
   LogProvider* log = nullptr;
-  SettingsProvider* settings = nullptr;
   SysProvider* sys = nullptr;
   FsProvider* fs = nullptr;
-  GuiProvider* gui = nullptr;
   HttpProvider* http = nullptr;
   TimerProvider* timer = nullptr;
   WifiProvider* wifi = nullptr;
   BleProvider* ble = nullptr;
 
+  GuiProvider* gui = nullptr;
   TouchProvider* touch = nullptr;
   ButtonsProvider* buttons = nullptr;
 };
@@ -82,7 +81,6 @@ public:
   bool applyPendingNavigation();
 
   LogProvider& log() const { return *providers_.log; }
-  SettingsProvider& settings() const { return *providers_.settings; }
   SysProvider& sys() const { return *providers_.sys; }
   FsProvider& fs() const { return *providers_.fs; }
   GuiProvider& gui() const { return *providers_.gui; }