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/driver.h

@@ -0,0 +1,145 @@
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "error.h"
+#include <stdbool.h>
+
+struct Device;
+struct DeviceType;
+struct Module;
+struct DriverInternal;
+
+struct Driver {
+    /** The driver name */
+    const char* name;
+    /** Array of const char*, terminated by NULL */
+    const char**compatible;
+    /** Function to initialize the driver for a device */
+    error_t (*start_device)(struct Device* dev);
+    /** Function to deinitialize the driver for a device */
+    error_t (*stop_device)(struct Device* dev);
+    /** Contains the driver's functions */
+    const void* api;
+    /** Which type of devices this driver creates (can be NULL) */
+    const struct DeviceType* device_type;
+    /** The module that owns this driver. When it is NULL, the system owns the driver and it cannot be removed from registration. */
+    const struct Module* owner;
+    /**
+     * Internal state managed by the kernel.
+     * Driver implementers should initialize this to NULL.
+     * Do not access or modify directly; use driver_* functions.
+     */
+    struct DriverInternal* internal;
+};
+
+/**
+ * @brief Construct a driver.
+ *
+ * This initializes the internal state of the driver.
+ *
+ * @param driver The driver to construct.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_construct(struct Driver* driver);
+
+/**
+ * @brief Destruct a driver.
+ *
+ * This cleans up the internal state of the driver.
+ *
+ * @param driver The driver to destruct.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_destruct(struct Driver* driver);
+
+/**
+ * @brief Add a driver to the system.
+ *
+ * This registers the driver so it can be used to bind to devices.
+ *
+ * @param driver The driver to add.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_add(struct Driver* driver);
+
+/**
+ * @brief Remove a driver from the system.
+ *
+ * This unregisters the driver.
+ *
+ * @param driver The driver to remove.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_remove(struct Driver* driver);
+
+/**
+ * @brief Construct and add a driver to the system.
+ *
+ * @param driver The driver to construct and add.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_construct_add(struct Driver* driver);
+
+/**
+ * @brief Remove and destruct a driver.
+ *
+ * @param driver The driver to remove and destruct.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_remove_destruct(struct Driver* driver);
+
+/**
+ * @brief Bind a driver to a device.
+ *
+ * This calls the driver's start_device function and increments the driver's use count.
+ *
+ * @param driver The driver to bind.
+ * @param device The device to bind to.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_bind(struct Driver* driver, struct Device* device);
+
+/**
+ * @brief Unbind a driver from a device.
+ *
+ * This calls the driver's stop_device function and decrements the driver's use count.
+ *
+ * @param driver The driver to unbind.
+ * @param device The device to unbind from.
+ * @return ERROR_NONE if successful, or an error code otherwise.
+ */
+error_t driver_unbind(struct Driver* driver, struct Device* device);
+
+/**
+ * @brief Check if a driver is compatible with a given string.
+ *
+ * @param driver The driver to check.
+ * @param compatible The compatibility string to check.
+ * @return true if compatible, false otherwise.
+ */
+bool driver_is_compatible(struct Driver* driver, const char* compatible);
+
+/**
+ * @brief Find a driver compatible with a given string.
+ *
+ * @param compatible The compatibility string to find.
+ * @return The compatible driver, or NULL if not found.
+ */
+struct Driver* driver_find_compatible(const char* compatible);
+
+/**
+ * @brief Get the device type of a driver.
+ *
+ * @param driver The driver to get the device type from.
+ * @return The device type of the driver.
+ */
+const struct DeviceType* driver_get_device_type(struct Driver* driver);
+
+#ifdef __cplusplus
+}
+#endif