render: add reusable renderer module and wire Thermometr example

include/display/renderer.h

@@ -0,0 +1,52 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct
+{
+    uint16_t* buf;
+    uint16_t width;
+    uint16_t height;
+    uint16_t clip_x0;
+    uint16_t clip_y0;
+    uint16_t clip_x1;
+    uint16_t clip_y1;
+} render_ctx_t;
+
+void render_begin(render_ctx_t* ctx, uint16_t* buf, uint16_t width, uint16_t height);
+void render_set_clip(render_ctx_t* ctx, uint16_t x, uint16_t y, uint16_t width, uint16_t height);
+void render_reset_clip(render_ctx_t* ctx);
+
+void render_clear(render_ctx_t* ctx, uint16_t color);
+void render_pixel(render_ctx_t* ctx, int x, int y, uint16_t color);
+void render_line(render_ctx_t* ctx, int x0, int y0, int x1, int y1, uint16_t color);
+void render_grid(render_ctx_t* ctx, uint16_t x, uint16_t y, uint16_t step, uint16_t color);
+
+void render_sine_wave(
+    render_ctx_t* ctx,
+    uint16_t num_points,
+    int amplitude,
+    float frequency,
+    int offset_x,
+    int offset_y,
+    float phase_shift,
+    uint16_t color
+);
+
+void render_bezier(
+    render_ctx_t* ctx,
+    const int* points_x,
+    const int* points_y,
+    size_t num_points,
+    uint16_t color
+);
+
+#ifdef __cplusplus
+}
+#endif
+