feat(led): 添加LED按键淡入淡出效果并重构LED条模块

添加了完整的LED效果系统架构，包括：
- 新增主题颜色定义文件theme_color.h
- 实现key fade LED效果算法，支持按键触发的渐变效果
- 创建LED效果注册机制和通用接口
- 配置17个LED像素与按键映射关系
- 将原有简单的周期性效果替换为基于按键事件的动态效果

CMakeLists.txt中添加了新的源文件路径和实现文件。

BREAKING CHANGE: LED效果从固定的周期性变化改为响应按键事件的动态效果。

src/led_effect/effects/led_effect_key_fade.c

@@ -0,0 +1,155 @@
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <zephyr/sys/util.h>
+
+#include "led_effect/led_effect.h"
+
+#define KEY_FADE_LEVEL_MAX 255U
+#define KEY_FADE_STEP_PER_TICK 12U
+
+struct led_effect_key_fade_state {
+	const struct led_key_map *key_map;
+	size_t key_map_len;
+	size_t pixel_count;
+	uint8_t default_brightness;
+	uint8_t level[17];
+	struct theme_rgb theme;
+};
+
+static struct led_effect_key_fade_state key_fade_state;
+
+static const struct led_key_map *find_key(const struct led_effect *effect,
+					  uint16_t key_id)
+{
+	const struct led_effect_key_fade_state *state = effect->state;
+
+	for (size_t i = 0; i < state->key_map_len; i++) {
+		if (state->key_map[i].key_id == key_id) {
+			return &state->key_map[i];
+		}
+	}
+
+	return NULL;
+}
+
+static int led_effect_key_fade_init(struct led_effect *effect,
+				    const struct led_effect_config *cfg)
+{
+	struct led_effect_key_fade_state *state = effect->state;
+
+	if ((effect == NULL) || (cfg == NULL) || (cfg->key_map == NULL) ||
+	    (cfg->pixel_count > ARRAY_SIZE(state->level))) {
+		return -EINVAL;
+	}
+
+	memset(state, 0, sizeof(*state));
+	state->key_map = cfg->key_map;
+	state->key_map_len = cfg->key_map_len;
+	state->pixel_count = cfg->pixel_count;
+	state->default_brightness = cfg->default_brightness;
+	state->theme.r = BLINKY_THEME_DEFAULT_R;
+	state->theme.g = BLINKY_THEME_DEFAULT_G;
+	state->theme.b = BLINKY_THEME_DEFAULT_B;
+
+	return 0;
+}
+
+static void led_effect_key_fade_reset(struct led_effect *effect)
+{
+	struct led_effect_key_fade_state *state = effect->state;
+
+	memset(state->level, 0, sizeof(state->level));
+}
+
+static void led_effect_key_fade_set_theme(struct led_effect *effect,
+					  const struct theme_rgb *theme)
+{
+	struct led_effect_key_fade_state *state = effect->state;
+
+	if (theme == NULL) {
+		return;
+	}
+
+	state->theme = *theme;
+}
+
+static void led_effect_key_fade_on_key_press(struct led_effect *effect,
+					     uint16_t key_id)
+{
+	struct led_effect_key_fade_state *state = effect->state;
+	const struct led_key_map *map = find_key(effect, key_id);
+
+	if ((map == NULL) || (map->led_idx >= state->pixel_count)) {
+		return;
+	}
+
+	state->level[map->led_idx] =
+		(state->default_brightness == 0U) ? KEY_FADE_LEVEL_MAX :
+						    state->default_brightness;
+}
+
+static bool led_effect_key_fade_tick(struct led_effect *effect, uint32_t dt_ms,
+				     struct led_rgb *pixels, size_t pixel_count)
+{
+	struct led_effect_key_fade_state *state = effect->state;
+	bool active = false;
+	bool visible = false;
+	uint8_t decay;
+
+	ARG_UNUSED(dt_ms);
+
+	if ((pixels == NULL) || (pixel_count < state->pixel_count)) {
+		return false;
+	}
+
+	memset(pixels, 0, sizeof(*pixels) * pixel_count);
+	decay = KEY_FADE_STEP_PER_TICK;
+
+	for (size_t i = 0; i < state->pixel_count; i++) {
+		uint8_t level = state->level[i];
+
+		if (level == 0U) {
+			continue;
+		}
+
+		visible = true;
+		pixels[i].r = (uint8_t)(((uint16_t)state->theme.r * level) / 255U);
+		pixels[i].g = (uint8_t)(((uint16_t)state->theme.g * level) / 255U);
+		pixels[i].b = (uint8_t)(((uint16_t)state->theme.b * level) / 255U);
+
+		state->level[i] = (level > decay) ? (uint8_t)(level - decay) : 0U;
+		active = active || (state->level[i] > 0U);
+	}
+
+	return visible || active;
+}
+
+static bool led_effect_key_fade_is_active(const struct led_effect *effect)
+{
+	const struct led_effect_key_fade_state *state = effect->state;
+
+	for (size_t i = 0; i < state->pixel_count; i++) {
+		if (state->level[i] > 0U) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static const struct led_effect_ops key_fade_ops = {
+	.init = led_effect_key_fade_init,
+	.reset = led_effect_key_fade_reset,
+	.set_theme = led_effect_key_fade_set_theme,
+	.on_key_press = led_effect_key_fade_on_key_press,
+	.tick = led_effect_key_fade_tick,
+	.is_active = led_effect_key_fade_is_active,
+};
+
+struct led_effect led_effect_key_fade = {
+	.ops = &key_fade_ops,
+	.state = &key_fade_state,
+};