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

Modules/lvgl-module/source/arch/lvgl_esp32.c

@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-3.0-only
+#ifdef ESP_PLATFORM
+
+#include <esp_lvgl_port.h>
+
+#include <tactility/time.h>
+#include <tactility/error.h>
+#include <tactility/lvgl_module.h>
+
+extern struct LvglModuleConfig lvgl_module_config;
+
+static bool initialized = false;
+
+bool lvgl_lock(void) {
+    if (!initialized) return true; // We allow (fake) locking because it's safe to do so as LVGL is not running yet
+    return lvgl_port_lock(portMAX_DELAY);
+}
+
+bool lvgl_try_lock_timed(uint32_t timeout) {
+    if (!initialized) return true; // We allow (fake) locking because it's safe to do so as LVGL is not running yet
+    return lvgl_port_lock(millis_to_ticks(timeout));
+}
+
+void lvgl_unlock(void) {
+    if (!initialized) return;
+    lvgl_port_unlock();
+}
+
+error_t lvgl_arch_start() {
+    const lvgl_port_cfg_t lvgl_cfg = {
+        .task_priority = lvgl_module_config.task_priority,
+        .task_stack = lvgl_module_config.task_stack_size,
+        .task_affinity = lvgl_module_config.task_affinity,
+        .task_max_sleep_ms = 500,
+        .timer_period_ms = 5
+    };
+
+    if (lvgl_port_init(&lvgl_cfg) != ESP_OK) {
+        return ERROR_RESOURCE;
+    }
+
+    // We must have the state set to "initialized" so that the lvgl lock works
+    // when we call listener functions. These functions could create new
+    // devices and services. The latter might start adding widgets immediately.
+    initialized = true;
+
+    if (lvgl_module_config.on_start) lvgl_module_config.on_start();
+
+    return ERROR_NONE;
+}
+
+error_t lvgl_arch_stop() {
+    if (lvgl_module_config.on_stop) lvgl_module_config.on_stop();
+
+    if (lvgl_port_deinit() != ESP_OK) {
+        // Call on_start again to recover
+        if (lvgl_module_config.on_start) lvgl_module_config.on_start();
+        return ERROR_RESOURCE;
+    }
+
+    initialized = false;
+
+    return ERROR_NONE;
+}
+
+#endif