Implement UI scaling and more (#501)

**New Features**
 * Runtime font accessors and new symbol fonts for text, launcher, statusbar, and shared icons.
 * Added font height base setting to device.properties
 * Text fonts now have 3 sizes: small, default, large

**Improvements**
 * Renamed `UiScale` to `UiDensity`
 * Statusbar, toolbar and many UI components now compute heights and spacing from fonts/density.
 * SSD1306 initialization sequence refined for more stable startup.
 * Multiple image assets replaced by symbol-font rendering.
 * Many layout improvements related to density, font scaling and icon scaling
 * Updated folder name capitalization for newer style

TactilityKernel/source/error.cpp

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: Apache-2.0
+#include <tactility/error.h>
+
+extern "C" {
+
+const char* error_to_string(error_t error) {
+    switch (error) {
+        case ERROR_NONE:
+            return "no error";
+        case ERROR_UNDEFINED:
+            return "undefined";
+        case ERROR_INVALID_STATE:
+            return "invalid state";
+        case ERROR_INVALID_ARGUMENT:
+            return "invalid argument";
+        case ERROR_MISSING_PARAMETER:
+            return "missing parameter";
+        case ERROR_NOT_FOUND:
+            return "not found";
+        case ERROR_ISR_STATUS:
+            return "ISR status";
+        case ERROR_RESOURCE:
+            return "resource";
+        case ERROR_TIMEOUT:
+            return "timeout";
+        case ERROR_OUT_OF_MEMORY:
+            return "out of memory";
+        case ERROR_NOT_SUPPORTED:
+            return "not supported";
+        case ERROR_NOT_ALLOWED:
+            return "not allowed";
+        case ERROR_BUFFER_OVERFLOW:
+            return "buffer overflow";
+        default:
+            return "unknown";
+    }
+}
+
+}