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/include/tactility/error.h

@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Avoid potential clash with bits/types/error_t.h
+#ifndef __error_t_defined
+typedef int error_t;
+#endif
+
+#define ERROR_NONE 0
+#define ERROR_UNDEFINED 1
+#define ERROR_INVALID_STATE 2
+#define ERROR_INVALID_ARGUMENT 3
+#define ERROR_MISSING_PARAMETER 4
+#define ERROR_NOT_FOUND 5
+#define ERROR_ISR_STATUS 6
+#define ERROR_RESOURCE 7 // A problem with a resource/dependency
+#define ERROR_TIMEOUT 8
+#define ERROR_OUT_OF_MEMORY 9
+#define ERROR_NOT_SUPPORTED 10
+#define ERROR_NOT_ALLOWED 11
+#define ERROR_BUFFER_OVERFLOW 12
+
+/** Convert an error_t to a human-readable text. Useful for logging. */
+const char* error_to_string(error_t error);
+
+#ifdef __cplusplus
+}
+#endif